future zamusa is most likely present zamasu that used a time ring (whenever he completes his plan) thats how he remembers goku and why he ain't need to fight trunks' goku. tho him jumping to not only a different universes timeline but a alternate one is iffy. unless time rings work in every universe regardless of if its your home one then ok , but how wld it get him to trunks alternate future and not the main dbz one'
(his universes green rings wnt work cuz their specificall tied to that universe unlike time rings and i doubt he stoe them from uni 7's kais so...)