Already put this in the discord, but I completely forgot to share it here.
Thanks to some help from Subquake, specifically knowing where to look in the DLL, I managed to add a menu option so the USER can select the maximum zombies spawned in the world in Single Player. For dedicated servers, this would be configured in the serverconfig.xml file.
I changed the default from 60 to 75, as I figure that should help with SP and RWG "zombies not spawning" issues. Max is set to 200. I don't recommend it... but... it's there. :D 100 should be the absolute max but may have potential performance issues.