Good clarification on what zaps are and their relation to lightning! They are just extra data sent that is optionally sent nostr when a lightning transaction happens. You could do the same for fiat transactions via stripe or something, or any other cryptocurrency. You could write a spec that sends an onchain zap when a bitcoin transaction confirms. You can do anything on nostr! nostr:note1calpf9mwheep9afnucm7svx8a9glqe0ga2jrjkx9gy7j626lwwwsnfmdd5