A Zero knowledge proof for set membership?
I think what you want is a ring signature. This is a signature mechanism that allow you to prove someone signed within a set of actor without revealing which one.

You may want to read https://link.springer.com/chapter/10.1007%2F3-540-45682-1_32 and https://github.com/Blockstream/borromean_paper/raw/master/borromean_draft_0.01_34241bb.pdf