Definitely fake, likely an import. The glossy looking, domed inlay is a big clue. I agree that this is block (plastic), as opposed to real stones. The silver feathers are machine made and it would be really unusual for Zuni artists to incorporate machine cast pieces into their handmade work. The open silverwork would be very unusual for Zuni work but I suppose not impossible. The generic, two letter stamped initials are also a clue. It’s very hard to trace something to a real artist with just two letter and the fakers know that so they pick random letters that seem like they could be attributed to a real artist.
Are you on facebook? Bree, from this forum, has started a group called “Identifying FAKE Native American Jewelry” which is really helpful in learning to spot fakes. Bree’s done a great job with the group. There is also another group called “Zuni Jewelry Let the Buyer Beware” which focuses on Zuni fakes and is also very helpful. I would definitely recommend checking out these resources if you’re looking to make more informed purchases.