Ozma's that hard?

[TheSpoonyBard]

Zidane is my item user because he can't do anything, his thief skill aren't useful here so I think he sucks in this battle

Thievery for 9,999 damage?

Steiner Shock is a guaranteed 9999 damage

Only if Steiner's normal attack deals 3,333 or more.

I'd use Zidane for Thievery, Freya for Dragon Crest, Quina for Frog Drop/Angel Snack and Eiko for Auto-Phoenix (99/256 chance, if I remember correctly) and throwing Dark Matters. You just need to hope Ozma doesn't use both Meteor and Curse in succession.

Completing the Friendly Creatures sidequest will make the battle much easier as well, as Ozma will become weak to Shadow instead of absorbing it, and can be hit with physical attacks (not that you should be using them, but it's useful if you have Counter, Eye 4 Eye and Bird Killer equipped).