Answer:
The Hitler zombie doesn't exist. Full stop
Well, I know this is unbelievable but yes there is one! If you a series of events in the right order during rounds, if you play in Nachet Der Untoten, instead of Hell Hounds, Hitler Zombie will show up. He takes alot of shots to kill, but in the end, you get a Max Ammo, like you do if the Hell Hounds show up, to get back what you gave