Zato is a power house if you can use him. To a new player, he is not the best choice, but he's useable. If you are new to him, start by figuring out how to use the Invite Hell move properly. Once you do, you should have no problems using Zato.

Moves List

Invite Hell - D,D+S or HS
Break The Law - QCB+K (Hold K to stay as a pool, release it to come back up)
Summon Eddie - QCF+P/K/S/HS (Depending on the button pressed, Eddie will come out with a different attack. This attack corresponds with the attacks that Eddie has.)
Eddie - Tiny Attack - (When Out) P
Eddie - Moving Attack - (When Out) K
Eddie - Anit-Air Attack - (When Out) S
Eddie - Drill Special - (When Out) HS (Forms a land mine looking like object which turns into a giant Invite Hell after about 5 seconds.)
Drunkard Shade - QCB+S
Damned Fang - DPM+S (close)

Overdrive Attacks

Executor - (in air) QCFx2+S
Amorphous - HBC,F+HS Megalith Head - (When Eddie is out) HCB,F+S

Instant Kill

Press All 4 Buttons to activate the "Attack Mode" then while in it:
Black In Mind - QCFx2+HS (close)

Combos

P, S, HS, D,D+S
Just follow what is said can you'll have an easy 4 hit combo.

Guilty Gear Mode Changes

Zato can play it safe now since he can now do the Invite Hell while he's in the air. It still comes out of the ground though. If you fly and then use it, the person won't be able to see it, so they'll get hit most of the time.

Gold Form Changes

Unknown at this time.