I really like this one, the idea is great yet I would have one Thing to fix.
If you have used Numpad 0 to put all Zombies @ crosshair Position and you wanna use it again on some other place, it kinda glitches out and does not work properly.
A simple fix is: If you press F8 and then Numpad 0 to unfreeze and relocate them it is possible but could be built in.
I hope you can do something with what I explained..