Zodiark was largely annoying cause death meant running through his not so fun dungeon which got tedious after awhile. With luck, its possible to kill him with a Quickening Chain if you activate it before he pulls up the physical pailing and get enough hits but... I was never so fortunate.

My strategy largely involved surrounding him in a triangle formation and then Scathing his ass. He's mean but I still feel that Ultima beats him out as a more challenging and nerve wracking fight. On the other hand, Zodiark is honestly one of the best summons in the game, especially since he does the highest most conditioned damage of all the espers and activating his summon attack is the easiest of the whole lot so you can really treat him like a more traditional summon a la FFIII-IX.