I've got PVZ spawn and dark horde as well. I modified a large majority of the zombie classes into slow walking dead types. My goal is to have a slow swarm suffocate the players after the runners break through. The issue is, the slow zombies lose interest after a while since they take a long time walking to the targets.
Is there a way to stretch out their attention span?

Also I've yet to see any special zombies other than the dark master, do I need to activate them somewhere?