I kept running into the same problem, trying to find Easter Egg guides for older maps, only to find dead links, missing images, or instructions that just didn't make sense. I got tired of it, so I made a website to fix that.
I wanted to make the definitive community resource for playing zombies.
I've finished Vanguard, Cold War, BO4, WW2, Infinite Warfare, and World at War so far, working on the rest. There are also solvers for the complicated puzzle steps, like Gorod Krovi's valves or the AOTRT chemical step.
It's free and open to contributions if anyone wants to help fill in gaps or fix stuff.