Limitations of the Zombie master

[hcobb]

The Zombie spell (along with Drain Strength) seems to unlock infinite actions per turn by a single wizard. She doesn't command the zombies, she is the zombies, seeing through all of their rotting eyes at the same time to disbelieve, etc.
So how do you overthrow a despot who is on every street corner at the same time? What tactics would you use?
The only thing that occurs to me is to ambush with instant squish or Remove Thrown Spell before your force was sighted.