Just finished my first ever zombies Easter egg. Der Eisendrache cutscene activated. Need a break from that game because it was like my 20th attempt. Finally got self medication gobblegum and was able to survive the boss fight.
Boss fight killed me the first few times I made it there cause I didn't realize you could dodge the keeper's shock attack. Panzer waves became easy when i was able to whip out a papped shotgun