The first time I fought Zisa I was not expecting him to appear and I was beaten senseless. He is the second easiest of the 4 superbosses though, Ice Titan is a pushover, Sephy is hard until you get to know his patterns and Phantom is just evil. :/

For fighting Zisa dodge roll is your best friend. Also summoning Tinkerbell after beating his arms the first time is very helpful for healing whenever he locks your Magic.