That tactic (omegaweapon's one) is based on having the right items. This walkthrough is practical and based on an aeon sac. I think it's also worth mentioning a few other points.

-Seymour has about 70,000 life.
-A holy water fixes zombie status.
-I'm pretty sure protect effects "Total Annihilation's damage bringing it down to a reasonable amount.
-Hastega gives you a hell of a lot more turns then you'd get without it.

There's probably stuff I'm missing.