@no offense, what are you doing? Set your zombie team up with:
Code:
disable_all_objects 2 1
That makes blue team unable to interact with ANYTHING. Can't pickup weapons, can't get in vehicles, can't use power ups (health, over shield, active camo)... That should be your basis for denying zombies access to things, not event_wpickup -> replace weapon.

All the zombies servers I've joined recently have really bad configurations. I should make a proper one and release it.