The loss is so ugly, not something Wilder wants to remember for the rest of his life but he can overcome this as he has one of the most illustrious careers, it's time for him to retire even if he wants to, two successive ugly loses is enough to call it over.
Wilder did not give an interview because he is still not getting over the loss but I'm sure he and his family will decide what his next step in boxing is, Joshua did come back from two successive losses but it's not from knockout and total domination that Wilder suffered so he cannot do an Anthony Joshua scenario.
After that fight, I looked at the stats of each boxer including the weight, reach, etc. and I saw that the Chinese boxer has a more than 70 KGS weight advantage, and I don't know if it's just me thinking like this, but I always believe that having that much of a weight advantage will have an advantage to the boxer in terms of his power punches.
I remember Garcia when he's I think 3KGS heavier than the required weight, and I believe it affected his power in his punches. Same with this one with Zhang and Wilder. Heavier fighter = heavier punches. That's what I believe, and for me, that's a factor why Wilder got knocked out in the 5th round but nevertheless, a loss is a loss and this is a bad way to end his career. I don't think that he will end his career with a loss though, and he might request for another fight in the future. This is his 2nd consecutive loss, and I don't think that he will end his career like that so expect another fight from him.
The question is what's next for both fighters. Anyway, his performance in his final 5 fights surely has an effect on his mental health so like what others said here, he must seek help from an expert.