
For people who don't know, there were at least 3 zombie maps scrapped from BO1, which were Paris, an early version of Shang Ri called "Temple of Doom", and a map called Veit Cong. The Viet Cong map concept was done by a Raven Software artist (Source)
Link to a Reddit post with some Vietnam zombie concepts
I know BO1 is 14 years old, but I would be surprised if they don't at least get inspired by these zombies