I think the reddit user someone else linked to pretty clearly explained the Monero side. Zcash has a bad reputation with darknet markets and the like that use Monero. Some of it deserved. ( I say this as someone who wrote original Zerocash protocol) https://www.reddit.com/r/Monero/comments/oui6zj/zcash_vs_mon...
Also, Zcash has optional privacy.
On the other hand, the decoy based privacy protocols Monero uses are not really private at all. https://slideslive.com/38911785/satoshi-has-no-clothes-failu...
Its cryptocurrency, everything is tribal.