Basically this is a more detailed version of the mondragon zvp guide. I learned most of what I know about the matchup from that guide and the ret replay pack. Their style is the easiest to copy and execute, and very hard for toss to play against.
Assuming the map is luna. Where you start out makes some difference. Cross positions pretty much render 2 gate rush useless. The 11 position is the worst because of the ramp position and slow mining. When you first spawn, send your overlord to the position vertical to you except if you spawn at 5. In that case send it to your left because you want to see as soon as possible whether the toss is going FE or one base. I only 12 hatch or 12 pool, some people 9 hatch but i've no idea how to do that. I scout with the 12th drone or until your first ovie doesn't see anything. Send your second overlord across from you and scout the other position that's not across from you with your drone. When you find where your opponent is send both ovies to his way.
Early Game Preparations
12 pool is the safest opening build as it is aggressive enough vs 9 gate or whatever that build is when toss sends one zealot out really early to harass, vs 2 gate, and lots of times vs FE because I don't think toss can 13 nexus and get cannons up in time unless they cut a lot of probes. It's also not terribe economically. If you see two gate, especially proxy, build zerglings constantly and chase his zealots back as far as you can before he reinforces. Use every larva as soon as it pops up to spawn more zerglings. If toss still wants to attack you and doesn't stop building zealots, get a sunken, but usually no more than one because you don't need it. If you have more than enough zerglings to deal with toss, split a couple from your group and backstab, hopefully you will be able to harass his base. never attack unless you have a zergling to zealot ratio of 3:1 (Midian's words, if it's wrong blame him). Get your 3rd hatch once you have the money.
If you 12 hatched which is what you should do most of the time unless maybe at 11. Vs two gate you should watch with your ovie how many probes toss brings. Get at least 3 drones to your nat, more if he brings more probes. And as soon as your expo hatch spawns, lay down three sunkens. Three is the safest, two can do most of the time. But usually good tosses will stop your drones from morphing into creep colonies, so you need at least three drones to be safe. If toss backs up sometimes you can just cancel two and leave one. It all depends on how hard the toss's rush is. Which is how early he builds his assimilator. Another very important thing is also to watch if he keeps building zealots or not after he gets gas. Sometimes toss will come out again when he should be teching. I'm a little tipsy so excuse the messiness of this guide. One thing for sure is, if you stop the two gate you're up, either unit wise or tech timing wise because toss sacrificed tech speed to try to hurt your early game eco.
What Each Different Toss tech means.
Assuming one base, toss will either build a stargate or citadel after core most of the time. A forge is also a possiblity to upgrade +1 really early which in that case as a crackling zerg you should match his upgrade. Doesn't matter if you don't match his +1 perfectly, the time when he has +1 when you don't will be very little. Toss can also try a goon range rush, it shouldn't be hard to tell by sending lings up the ramp and scouting with ovies to see if goon range starts researching.
If toss builds a stargate, you can either get a hydra den or evo for spore. Hydra den delays your lair by a bit but you'll be defending your ovies with units rather than static defense, which means you won't be fucked if toss scout rushes. When you see a stargate warping try to hide an ovie nearby while scouting with the other one. If you see a citadel before your ovie is killed that means toss is playing normal one base expand. If you don't then it usually means toss is hiding something, most likely a robo. Vs that research hydra range and protect yo base while keeping lings outside his. Get a spire after your lair is done morphing. Vs goon rush just mass lings or mass hydra and flank his army when he comes out and backstab him to death. It's a stupid rush unless toss can hide it.
If toss builds a citadel then archive with one or two gate. Keep an ovie near his natural and you can either try to kill him before he comes out or play it safe and tech normal. If you want to kill him early, start researching ling speed and mass lings, make sure you HIDE YOUR TECH. whenever toss comes out doesn't matter what kind of rush he's doing, if he doesn't have like 10 dts you shouuld be able to kill all of what he has and win. You can also go three hatch hydras in this situation, no matter what toss should be punished for not scouting. If you want to play it safe then just tech normal.
Rush vs No Rush
Off of one base citadel archive tech, toss can either expand early or expand late. Since your ovie will already be dead, you should know which one by experience. If he expands early, then he won't have enough units to rush and you can power safely or even try to kill his cannons if you teched fast. If he expanded late he is rushing. Brace yourself for it either by getting some lings or hydras or sunkens, one very important thing I will stress over and over and over again is always look for an opportunity to backstab. Backstabbing makes opponents dizzy (lastgosu's words). When toss goes for an one base rush you should always try to backstab. Usually toss will wait till his cannons are done warping before attacking though.
What you should be doing.
3 hatch, get gas, if you're not going all-in then play normal. Use a den or spore to fend off the sair. Doesn't really matter when you get gas just don't get it too late or too early. Lair, ling speed with next 100 gas. Pump a lot of drones. In zvp the build orders aren't nearly as restricting as zvt because there's so many variations as to what toss can do. So when you build zerglings, how many, should be dependent upon what toss is doing and whether if he's expanding or attacking when he comes out. Just remember to have units for harrass or to defend.
After Lair
When toss gets stargate, the purpose of it is to scout, kill overlords to slow zerg down, and maintain some map control with dts. That means dts will kill your stray lings, dts will be at your expos. Watch for that. However the more dts toss gets for harass the more gas he'll spend the less templars he'll have. However as zerg all you have to worry about is expanding.
I'm still not completely sure about this. I advise expanding to mineral only but some players expand to another main's nat. A min only is closer, easier to defend, but another natural has a gas and you will only have to sunken one other spot other than your own natural. However you really don't need three gases until you morph your hive because it will create a mineral/gas imbalance. That plus the fact a min only is closer makes me still think that min only is the better decision.
When your lurkers are done, the things you HAVE to do are, get SIX hatcheries. UPGRADE, and get a SPIRE. There's gonna be a dt at the min only you want to expand to. If toss is not rushing, you can get a couple hydras and send a slow overlord that way, protect it with your hydra/ling and expand as soon as you can even before lurker research. Most of the time I get a spire right after lair while researching lurkers for deception and for scourges to kill that sair. The downside is less lurkers and not being able to research ovie speed as quickly as you'd like. When your lurker research is done, morph a good amount, like five i'd say is a good number. If toss is still not back in his base and is containing with say zealots and archon, either sneak out and backstab his base with lurker ling while defending your own base of course, or try to damage his force with your lurker/ling force. Either way he's made a mistake. He can't detect lurkers. If toss is back in his own base, contain with your lurkers, expand to min only if you haven't already done so, get six hatcheries total and send your lings to scout all across the map to make sure there's no hidden toss expo. I recommend getting ovie speed for scouting but it's not required as it slows down your hive. If toss really does not have any muta defense at all, switch to mutas, but in most cases, get a queens soon after your lurkers are out and tech to hive. The exact timing is dependent on how far you're ahead or behind and whether you can afford it. Either way your hive should be done very early. Like before 10 minutes.
Upgrades are very very important as they're the only reason you're using your zerglings. Get caraspace upgrade as soon as you can, add another evo after lair. Be ahead on upgrades at all times, never stop researching. (INCONTROL TAUGHT ME THAT !!!!!!!!!!)
At this point, which is after you're containing with lurkers, toss will be busy getting a robo and being paranoid. Pump as many drones as you can afford, there's no exact number, just don't get too little or too many. Pump lings the rest of the time and rally them to where your lurker contain is. Spread your ovies out, get scourges, watch for shuttle. Form a ring around his base with your ovies. This is when you can tell if a toss is good or not, how fast he breaks out of the contain and in what manner. Keep detection everywhere so you can scourge obs, if you group scrouges with lings there's no way toss won't lose the obs if you have it in sight and if he doesn't have obs upgrades. Move lurkers that have been stormed back. Don't get anymore lurkers unless you HAVE to buy time for cracklings or upgrades to finish researching. Five is a good number but it really depends. If you get more lurkers you will be delaying your hive, ultras, cracklings. By five lurkers I mean have at LEAST five at all times, if a lurker gets killed replace it. Also if toss masses only zealots, get more lurkers, don't save your gas, if toss masses mostly goons, mass lings, (courtesy of royce ). In a lurker contain your lings will deal most of the damage. At about whenever your hive is almost done assuming you're still on equal footing with the toss, expand again to another gas. THIS IS WHEN YOU'RE THE WEAKEST, when you don't have cracklings and toss is almost about to break out. You army at this point should be about five lurkers, a few scourges and a million zerglings.
One possible scenario is if toss gets a robo before storm and wants to break out asap, do not freak out, retreat with your lurkers, turtle with sunkens and either get more lurkers or switch to mutas if toss isn't aggressive enough. Just remember that it is a stupid build.
Late Game
If toss doesn't break out after your crackling research is done then there's no hope for him. Keep rallying lings, watch out for shuttles and keep expanding. Get an ultra den so you can spend all that gas. If toss has broken out, sunken if needed and wait for ultras and cracklings. Keep like a couple lings near the toss min only so you can harass his attempt at expanding. Make sure if you attack the toss army that you attack it with ALL of your units as he will have all of his. Other than that, you should be sitting on 3 gas and min only to his 2 gas and min only. RESEARCH HYDRA UPGRADE. Throw hydras into your army so you're not vulnerable to a sair switch. Research drop. And just harass one place, attack another, drop his main, attack his expo. Use defilers if you can. Rally all your units to one spot. If toss doesn't go for a sair switch or doesn't get reavers and doesn't expand aggressively enough you shouldn't lose if you don't fuck up. You really don't even have to micro your lings. When you win, nine times out of ten the protoss will whine about zvp imba when they should've broken out hours ago. Don't mind it. Enjoy your victory.
Small rep pack http://download.yousendit.com/CDB6DDFE5A7D2F3B (don't do what the zerg does in the first replay. I was in my ret copying stage then. If you don't have amazing unit control and macro you need all six of your hatches for unit production. Don't try to be greedy and take that third gas. I lost waaaaay more than I won trying to expand at min only AND a gas natural.)
Hope you enjoyed that, this is a very rough first draft I will correct it whenever I can. Thanks for reading.