Guide and mulligan after +50 votes. EDIT: threshold has been reached.
Mulligan: Try very hard to get 1-drops. If you have coin, you can keep Councilman against slow deck, and also dire wolf alpha/ravasaur runt if you double 1-drop turn 1.
-Mortal coil -Shadowflame -Feeding Time
+Crazed Alchemist (instant kill totem/doomsayer and easier trade with taunt warrior)
+Argent commander (can also Leeroy but argent is better at trading with divine shield)
UPDATE (May 20):
-Argent Squire > 2 Soulfire. I hate to use discard in the pure zoo, but extra reach for lethal and removal is necessary and very important in this meta and sometimes too much 1-drop is overkill. I still insist not to use Doomguard though.
-Devilsaur egg > Additional Eggnaper. Devilsaur is 3 mana lost tempo. 0/3 does nothing and too slow in this meta. Eggnaper is more pressuring and valuable since it's deathrattle synergive with the deck and weapon class usually against killing it unless they have1 damage aoe. It's a neutral ratpack made for zoo <3
-Abusive sergeant > Dark Iron Dwarf. 1 sergeant is enough and 4 attack is solid against Priest.
-Frostwolf Warlord > 2 Nesting Roc. Taunt is very important to keep your key minions alive (Knife Juggler/Councilman) and it is easy to have atleast 2 minions by turn 5 as zoo. Frostwolf is solid as an aggressive version of it (Bittertide Hydra-esque) but is does not protect your other minions from enemy attacks and 4/7 body is usually good enough.
-1 Ravenous Pterrordax > Sea Giant. You can still use frostwolf in this spot or even keep using 2 pterrordax but I think 1 is enough because this meta is very aggressive and sometimes you don't have a good token to eat with it (Like eating councilman is not great). Sea Giant is good craft if you die hard zoo lover (1 is enough). It can be 1-4 mana 8/8 if you and your enemy floods the board and it's cost is flexible compared to warlord. Always flood the board first and trade last if you want to drop Sea Giant on the turn.