Easy PP Points (quick Lv.50)+easy Zombie Genocide Achievement:

Go to the entrance plaza then go upstairs. Go to the end with the bee then go to the door marked "Exit". This hallway is the one from the very beginning that Otis sealed off. It is a dead end but has a lot of zombies that will continuously respawn. This allows you to get a lot of kills quickly,or go to the uderground tunnels with plenty of queens (if you use up all your queens get load of necture smoothies and goback to where you killed all the zombies then drink the smoothie and kill loads more zombies with a katana/mini chainsaw then you will have more queens to use.