Ultraman has returned, but he won’t be able to stop Zeref. Zeref can absorb the life force of people just by existing. Ultraman’s time limit is already quite brief so this won’t do him any favors. He has some reasonable strength and speed, but it isn’t at a level where Zeref would be nervous. He’ll casually just take Ultraman down with a single punch or two and that would be the end of that. Zeref wins.