This Zoo list I used to climb to legend this month. It is more or less standard Zoo list, but it has at least 6 cards difference from common Zoo lists that are recognized by hsreplay, so I would say that those are suboptimal.

Main differences  from other decks:

• I don't run Neferset Thrasher, what I found is that it is very deadly, problem is it is usually me who dies to opponent's burn because downside of Neferset is way too much against Hunters and most of other Midrange and Aggro decks he just doesn't work.
• I don't run Magic Carpet, because it is relic of the past and according to stats is actually not good in Zoo
• I don't run Scarab Egg, it is just way too clunky and generally not good enough.
• I do run all 3 Dark Pharaoh Tekahn, SN1P-SN4P and [Hearthstone Card (Soularium) Not Found] because they are just good legendaries in zoo it seems
• Probably some cards can be replaced for Knife Juggler I just didn't find place for him, but maybe Sea Giant isn't good enough, often he giant is just too late. I do like sea giant, it does manage to find some breakpoints against certain types of removal or board states. In some match up you do want to go tall.

Mulligan guide

So mulligan is fairly simple you just search a curve, whenever I don't have a 1 drop minion I just mulligan everything. (Sinister Deal isn't a 1 drop it is essentially a 2 drop at best)

Then if you do have 1 drop then keep a 2 drop not all 2 drops are equal so try to find some synergies between your 1 drop and 2 drop.

Consider keeping packages. Packages are:

Mecharoo + SN1P-SN4P

EVIL Recruiter + any lackey generator (especially good on coin, just keep coin and lackey in hand until turn 3)

Serpent Egg + EVIL Genius

Crystallizer + Diseased Vulture (Though I wouldn't recommend keeping vulture unless you are on coin and have some other 1 drop and some 2 drop, basically vulture is good, but good curve is more important)

Card replacements

If you are missing any cards I suppose Knife Juggler should be a good replacement for pretty much anything, except 1-drop, if you are missing some 1-drop then replace with Abusive Sergeant.

Game examples

Here are some wins agaisnt various decks:

https://hsreplay.net/replay/dPSFkQW38HZFhuhdmVXKyX  - control warrior, make sure to have a tallish board to not play into board clears too much...

https://hsreplay.net/replay/ReL9CtVCUbEHbTTUPyK69o - quest druid, overwhelm them before the can go off much.

https://hsreplay.net/replay/yZiPQaWonajxa6Msg7uG5W - against hunter tempo is king, don't be scared to value trade.

https://hsreplay.net/replay/yLS2hny2ZWhU5PKhdP6ZyX - against mage you usually want to overwhelm them early, but don't give up if you didn't manage to do it like in this match, just make sure that Blizzard and Flamestrike and Reno don't just wipe you out.

https://hsreplay.net/replay/vwaaFKS3pHDeumknmAcHUg - against murloc paladin make sure that you board is very wide so that tip the scales doesn't just destroy you... though sometimes board clear from spell lackey can help.

https://hsreplay.net/replay/fBAyJMnzX4LEBDygnw8SEF - against quest paladin make sure to pressure them enough so that their completed quest doesn't do much before they die...

https://hsreplay.net/replay/4GTVChoEVdYFJCM9Pxf6Sk - against OTK paladin you usually should win, just make sure that shirvallah doesn't live.

https://hsreplay.net/replay/LSvKEK55m9pXUD93SM68MF - quest priest for the most part does nothing so just make sure to kill them quickly before big stuff comes. also playing egg on turn 4 helps against mass hysteria a bit.

https://hsreplay.net/replay/xB5UJSNWksnkxpRsKSrCxR - against inner fire priest, make sure none of their stuff lives...

https://hsreplay.net/replay/HxjxwHTtvN2z97YKFimJvh - against aggressive rogue make sure to protect you health total as much as possible, their burst is insane you need to defend yourself against rogue for the most part.

https://hsreplay.net/replay/vvpDZTAWNZaGqxSrPWBqYU - quest rogue, play for the most part same as other rogue, just you are a lot more likely to win, as they don't pressure you as much.

https://hsreplay.net/replay/XfxauGHXdY7WgAyxK73Vfh - against overload shaman, tempo is king

https://hsreplay.net/replay/TRXnUTojbdk4TvbVqJo3EC - against murloc shaman tempo is also king, just make sure to kill any murlocs first and then other minions

https://hsreplay.net/replay/aMSPvUGWQx7hXaakRYtfSm - against quest shaman, yet again tempo is king, though you might need to get lucky, match up is tough

https://hsreplay.net/replay/gxKA6FGYXq2okZjQ9U2qKJ - mirror is of course also tempo game, lackeys are your main weapon, make sure to use them well.