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This episode does not exist. Zecora is the only Zebra that has appeared in the show. Other than her, the only one we met was Braze in Rainbow Dash's book.
You probably were thinking of something that had came from a fanfiction, most likely animated afterwards.
Or alternatively, in S 5 E 25-26, which includes a universe caused by time travel where the ponies are all tribe-members.

In My Little Pony: Friendship Is Magic, was there an episode with a whole group of zebras that were doing this religion or something and Zecora or some other zebra was the sort of "leader" and was holding a pink flower in its mouth?