Like I said I've been really ill and so for the last month or 2 I've been out of action =( BUT! Although I'm still in hospital and still very ill I'm starting to feel better so I've got some time to work on updating this guide (and maybe even look at writing another!?). It might be a little while since this isn't the easiest place to work, but I'll get it all up with what you could, should and shouldn't run in zoo, and how to play it properly.
So. This is what I would call the consistent version of the deck, but I'll also go over the cards you can put in to make the greedier version, which is more popular in tournament play where decks focus on trying to crush one or two games instead of climb ladder consistently. Let me give you the 'loa'down (See what I did there? :P) on a couple of the changes from the previous deck.
The deck needs this slot to be a turn 1 play in my opinion to have the right balance. I also think that card should be a deathrattle minion. That leaves you a choice of gnome and Zombie Chow. I think both are actually quite even but in this meta where the Naxx cards gave a lot more decks early plays to deal with zoo, Chow feels bad often enough that I'm running the gnome instead. Sorry Trump.
I really like tech cards like owl in this meta but I don't like dead cards in zoo. I'm not sure whether one or two owls is correct, but I think if you aren't running other potentially dead cards like Power Overwhelming then two is OK. I may change my mind on this when I get an all owl hand and a shift in the meta could definitely put owl back out the deck considering the minion itself would be bad for 1 mana let alone 2.
Sadly the cleric has fell by the wayside recently, but once I removed the Void Terrors I felt the deck absolutely needed a 3 instead of, for example, another Abusive Sergeant or Dire Wolf Alpha. This spot is an opportunity to fit a tech card if you like, although that's mot really the est way to ladder. For example Big Game Hunter for hunting big game, Blood Knight if you're running into divine shields, Earthen Ring Farseer to improve your trades/heal against combos and aggro, and if you're a manly manly monkey, King Mukla. However, the most consistent 3 drop after Harvest Golem, in my opinion, is the cleric. Scarlet Crusader doesn't have an immediate impact and has some pretty painful counters like Blood Knight and Earth Shock. There are other options with their ups and downs but for ladder I would always go for consistent.
Which finally brings us to the real top man of Naxxramas (sorry KT). I wasn't sure whether his board presence was enough for what zoo often considers going into late game, then I realised I was stupid and immediately started playing Loatheb. While I wouldn't say Loatheb is the best card in the game, I am struggling to think of a SINGLE deck that I wouldn't want him in. Not one. The pressure he can put on while the opposing control deck is lining up their removal. The options it takes away from an opposing aggro deck trying to snowball the board (although not really zoo). The halt it puts on a combo decks blowout turns. And finally the reason it's in zoo, what it does for you. It can single handedly snowball you into a winning position, because if you are in a decent position on board, as zoo should be, and you drop this guy, suddenly it becomes very difficult for most decks to find a response, and you can often get game winning trades or damage of the back of it.
So what if you wanna get greedy?
Putting in the Power Overwhelming/Void Terror combo is one way to add an element of risk/reward to the deck. I've also seen people running cards like Voidcaller, Acidic Swap Ooze, Dancing Swords, Deathlord, Flesheating Ghoul, Questing Adventurer, Raid Leader, Cult Master, The Black Knight and Ragnaros the Firelord. Some of these cards are better than others, some are greedier than others, but ALL of them are great ways to get you hilarious HUGE wins... but also even bigger loss streaks. I do not recommend, although a couple could find their way to a tournament deck. Wanna build a greedy zoo deck for ladder? I have one word for you. Mrrrghlgrglglgh!