Revivfy doesn't work as the spell to create zombies, animate dead, takes an hour and revivify can't return beings that were dead for more than a minute. If the undead is created in a faster method, it would work by RAW.
True resurrection was updated and now says that if they were undead they return to a non-undead form, which implies that resurrection won't do the same, true resurrection means that it's always possible to get someone back, if their souls is free, despite the extreme price
