This is just something quick and dirty that I posted in a thread that got closed. I liked how it turned out so I decided to conserve it for later usage. Enjoy!
In that Match-Up Protoss isn't in the role of "My Hellions kill 1/3 of your drones". Instead we're trying to achieve something along the line of "I'll scare you so much that you won't even have 1/3 of the drones you'd like to have".
To do that we utilize certain strategies:
0. The Generel Idea of moving out
Biggest fear in the Protoss mind in PvZ is "Oh my god, if I leave my base I get swarmed to death". Well, you are either doing a.) a Stargate opening (Which will make you know whats going on, so you don't have to worry) b.) a DT opening (refer to a.)) or you are going for a sentry heavy expansion.
And in that last case a lot of players are scared to lose their sentries, but actually thats not neccessary. With the FFs from 6+ Sentries you are able to close off your path on nearly any map to make for a safe retreat. So whenever you encounter a zerg army thats too much to handle then just throw down a couple of FFs and retreat. This should give you much more security in moving out of your base and this is really important for whats coming.
1. Deny Map Control
Regularly the Zerg tries to get a good read on what you're doing with spreaded units and Xel'Naga-Towers. Some Zerglings will wait in front of your choke, an Overlord sitts over your third and he's devoted to get the Xel'Naga-Tower. Clear those out! Always dart at least a little bit out of your base, try to clean up every spotter you can find and go to the Xel'Naga-Towers regularly (If the Zerg tries to ambush you then refer to 0.).
What you are doing with this is you're denying the Zerg knowledge - and he needs this knowledge to judge when and how much units he needs to get to be safe from your attacks.
2. Clear out creep
As soon as you get your first Observer it is neccessary that you start to push back the Zergs creep. Try to kill as many of the tumors as possible - I regularly use three stalkers for that with the Observer slightly ahead of those so I can retreat with them quick enough to my army that should be at a utilizable choke (e.g. at Xel'Naga Caverns I leave my army behind the rocks of my gold expansion while my Stalkers clean out the Tumors around the Towers).
3. Fake pushing
Whenever you go to clean out Xel'Naga Towers you can dart in the general direction of the Zerg, utilizing your FFs to get away if he tries to overwhelm you, from time to time it can be a good idea to let the Zerg have a Tower just to let him see how you march in his generel direction (The effect of this gets multiplied when you bring a probe along and slap down a proxy pylon in front of his base).
4. Any Harrassment that your build offers
Phoenix, DT, Blinkstalker, Immortaldrops, you name it. Whatever your build offers you to play around with can be used