Here are 10 cards that own zoo lock. I win about 80% of the time vs them and am rank 5 thus far this month (ran out of gold rewards tonight :-/) Notice a lot of these can be doubled in your deck (and should be) so your chance of pulling at least a few of them is pretty high hence the win rate.
Innervate - You really really need to get something big out or he'll run over you with a lot of small crap. Getting a big 7+ minion out is a game changer on turn 4
Wild Growth - same as above, if you can use wild growth turn 2 and get tas dingo turn 3 you're in good shape, he'll have to clear his board or burn a soulfire (and another card since his hand won't be empty yet) to take care of it. Then next turn you can drop a bear druid, or swipe, or any number of other things.
Swipe - this card is so clutch vs zoo, especially if you keep stuff he drops at 1 health when you have it in your hand. Don't hit that knife twice to kill on turn 2, hit him once, then hit the other 2 HP drop once, and swipe the void. Sometimes he will play around this and buff any 1 HP minions with his sun cleric, when he does that the best possible solution is a thalnos plus swipe if you can. A clutch thalnos drop followed by a swipe is almost always a game ender.
Tas Dingo- The 4 cost troll taunt is so important to this match up, not having 2 of these is insane. They almost always either take one of their 2 soulfires and trade 1 for 1, or they trade 2 or 3 for one. Either way a great use of 4 mana.
Keeper - The keeper is so key on turn 3 (or earlier with growth/innervate) because it lets you hit that knife thrower even when he drops void or shield bearer to keep him protected. He's also good vs imp. Really all the early minions are 2 HP or less so he's pretty perfect all around.
Baron Geddon - This is a late game play, but he's just amazing vs any kind of rush. He literally will clear the board every round of pretty much everything other than doomguard. That doomguard he will almost always have to trade 1 for 1 for baron which is advantage you. You have other big stuff, he only has doom guards and probably loses cards to play him. IMO this is the absolute best legendary vs rush.
Ancient of War- If you can bait out his soul fires and keep the minions to a reasonable level (3 or less) this guy is a game ender. He needs to clear his board and then some to do 10 damage. His only real recourse is doomguard and even then it only gets him halfway there. If you have 2 of these or can faceless one that is above 6 health almost all locks will auto concede. He's just their bane across the board. His only weakness is silence, so if you can bait a silence on tas dingo or thalanos that's pretty key. The last thing you want to have happen is to put him out and have him turned into a 5/5 while they smash your face. That is incidentally why baron is better than he is, he offensively clears the board instead of waiting for them to attack you and die on their own.
Mark of the wild - This is key on keeper and other non taunt minions because it turns them into something the lock has to trade 2 or 3 for one on. A really cluth play is to faceless manipulator a doomguard, mark of the wild him, and kill off their doomguard while still having a 7/4 taunt minion left over. The best play of all time if you have innervate or are late game is to play mark of the wild on their doomguard, faceless him, then pop him with a big game hunter. That is pretty much a game ender if you can pull it off.
druid of the claw - playing him in bear form early is pretty awesome if you can get him out. The best time to play him is if you can wild growth with the coin leaving you at 3 mana next turn, then innervate to 5 and play this guy. Really though any time he will almost always trade 2 or 3 for one and just ruin their day. He's a great place holder until you can get the tree of win out, and unlike the tree his stats don't go down if he gets silenced which is a nice bonus.
Sylvanis - She is pretty much a guaranteed 3 for 1 or 4 for one because of her stats and her death rattle. The lock will almost always have minions out for her to steal. Even if he doesn't attack her you can mark her to make her a target or just kill her clearing out minions and force the death rattle. The normal strategy of not playing minions and clearing her with a spell just isn't an option which makes her stronger than normal.