Here are a few links to help you do Easter egg 2 in zombies

https://www.gamepur.com/guides/how-to-complete-the-second-outbreak-main-quest-easter-egg-in-call-of-duty-black-ops-cold-war-zombies   (Walk Threw from the beginning)

https://www.reddit.com/r/CODZombies/comments/o26hbn/outbreak_ee2_sanatorium_mystery_boxbunny_locations/    ( Where to find the Bunny )
 
              I hope this helps you all out with the hunt.

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Cool tks