I'm flying out to London tonight, but in the week leading up to I played ladder harder than I ever had previously (last season peak, rank 9). So this season I peaked rank 1, 3 stars. Zoo has a lot of small changes that you can make to gear it more towards aggro / control. Shadowflame / Hellfire / Leeroy + Power Overwhelming / Elven Archers / Mortal Coils, are all cards that can be swapped in and out. I think of zoo generally as an aggro deck that plays as control. This is the case because Zoo is THE benchmark for a deck being prepared against aggro.
Has anyone else seen the recent King of the Hill? Xixo's Lorewalker Cho Zoo, man.
LonelyNess I don't know about some of your matchup analyses... Control Warrior actually generally plays two copies of Whirlwind, especially with the addition of double Azure Drake to the build. The cards you see Control Warriors run a single copy of are either Slam, Armoursmith, Cleave, or Wild Pyromancer. The last two additions are recent, in order to accommodate aggro (mostly zoo), some variants also run Taz'dingos over Kor'kron Elites. Basically, Control Warrior should eat zoo alive. That deck is designed to beat aggro (which is pretty much synonymous with zoo).
Burn Mage doesn't contest the board by having big Taunt minions OR an equal board size??? It contests the board with AoE / Freeze / Doomsayers / (SOMETIMES GIANTS, that aren't taunted). You can count Mirror Image as 'Taunts' but they achieve nothing vs. Zoo, anyway. I'm not too familiar with this matchup, so I won't say anymore.
Handlock can go either way, but I believe Zoo is favoured. It depends not only on their draws, but whether or not they pack double copies of tech cards. Early Watch + Sunfury can really mess you up. As can double copies of Hellfire, or even single copies. I see newer generation handlocks running Taz'dingos, too. If you hit face and they can only clear your board once before Taunted Giants hit the field, you're in okay condition. If they clear your board twice, that's when you're probably screwed.
Priest has some of the best AoE in the game, provided you're using Wild Pyromancers. Auchenai + Circle / Holy Nova / Pyromancer combos is more than enough to clear Zoo's board over, and over again. Priest also has the sustain to take it late vs. Zoo, where the latter automatically loses. Of course, Priests are notoriously unreliable and can lose to anything on any day. However, to say that Priest is a free win, or even that Zoo is a bad matchup for Priest, is a stretch.
Finally, ramp Druid has a very, very good fighting chance against zoo. A lot of board clear, strong taunt minions, and a way to accelerate curve. The Millacle druid, which I've played between ranks 1-5 successfully, auto-loses to zoo, unfortunately. Token druid, probably the only other variant (discounting subset versions, etc) of Druid, also has very strong potential to do well against zoo.