Terran and Protoss both have become very versatile on the battlefield. They have many tactics to surround, and change up the way the battle turns out. Let me name a few of these.
Stalkers: Blinking is an easy way to surround the enemy. You can go up and down cliffs, pulling off surprise attacks.
Vikings: Also a good way to surround the enemy. You can pull off surprise attacks, and get behind the enemy quickly.
Colossus: Ignoring cliffs, these beasts can easily surround an incoming force of Zerglings, approaching your Immortals. Being sneaky enough, you can go around the battlefield via cliffs, and backside the enemy.
Reapers: 'Nuff said.
Zerg don't have much that would be called versatile, or atleast compared to the other two races. Yes, they have nydus worms. These aren't quite versatile however. Sure, once they are set up they are, but getting behind the enemy using these is a different story. Plus, I can't imagine people getting a Nydus all prepared in time to stop a force of Stalkers.
All Zerg ground units, while burrowed, are mobile, but only while under creep. This would make a big emphasis on spreading creep. You will now have to think about positioning your Zerg force before hand, and securing a safe place of creep.
Imagine: You have constructed a few plots of creep outside your first expo. You are attacked by Stalkers. You burrow about a fourth of your Zerglings, and move the lings to the other side of the Creep plot. The Stalker's blink micro isn't turning out to be as effective now that they're surrounded.
I was imagining moving speed to still be pretty fast, else it wouldn't prove to be useful in the first place. (First group of lings would be dead by the chance you get to move your burrowed group and unburrow). It would be really creepy moving around in a Zerg base. Zerg could be crawling behind your back right now, ready to spring out.
Anyway, how do you guys think this would work?