ellement115 is actually real, its what made the zombies what they are and is what they put in the ray gun and wunderwafle. 115 came from asteroids like the one on shi no numa, also the wunderwafle is based on a real gun that the Germans tried to make but couldnt.
all the numbers on the walls throughout all the zombie series mean something. like some are from verses from the bible. numbers are dates from real life events. some add up to 115 if you put them together in the right way. some events mark days that asteroids hit earth, one above russia and another above pennsylvania.
the radios and stuff in the game are the story. the mystery box, dogs, teddy bear, creepy girl voice are all explained in the radios but you really got to put everything together to understand completly.
just watch the video cause theres alot more that i cant remember.