I think Wilder is a more effective one punch power puncher but Zhangs style is a more effective against fighters who are trying to knock him out. Maybe if you give Wilder some of his old speed back it goes differently. No question Wilder fought Zhang at the worst time. Not only was he slower but he was coming off the Parker fight and needed a confidence booster instead of a unique challenge. Wilder is better then Joyce.
Basically. And also... That Zhang hits hard and his victims don't see it coming - that makes the impact much worse. Would Joyce be able to take Wilder's big telegraphed bombs? Maybe not, but it's hard to be sure... In many ways, we know Zhang is seriously powerful precisely because he has hurt (and stopped) guys we know are extremely durable - stopping Joyce confirmed that he's definitely legit powerful, as did badly hurting Parker. With Wilder it's less clear - some of his opponents were fairly durable, but none were famous for it... Did he look more powerful than he was because he never met a known A-grade chin? Probably - but how much is the big question.
Or in other words, Zhangs more capable against opponents who aren't overmatched and/or just trying to survive? I mean, I can go with that... I guess the age old question is what we're even talking about... There's obviously a big difference between talking about the power a fighter could throw at a static target (or even a punching machine) on the one hand, and the power they can realistically throw against fighters around their own kind of level - and the higher the level, the harder it gets to throw full power at all. This is the problem with going too far with Wilder's power - he spent most of his career hiding from fighters his own level (whatever you want to label it) and fought guys who mostly weren't very good... And that will always make a fighter look more powerful than they are.