QIf an opponent has 7 cards in their cemetery, and I summon an Octrice, Omen of Usurpation and Zealot of Usurpation from my cemetery with this follower's On Evolve ability, can I put the top card of my deck into my EX area with Zealot of Usurpation's Fanfare ability?

AYes. Since both Octrice, Omen of Usurpation's Fanfare ability and Zealot of Usurpation's Fanfare ability trigger and become pending at the same time, you may resolve them in any order.

To put the top card of your deck into your EX area, you must resolve Octrice, Omen of Usurpation's Fanfare ability first to bring the number of cards in your cemetery to 9. You then resolve Zealot of Usurpation's Fanfare ability to bring the number of cards in your cemetery to 10, satisfying the "if there are at least 10 cards in opponents' cemeteries" condition.