Regarding Zhang's age: Most Fields medalists these days are very close to exceeding 40 years. Wiles himself just a special silver medal, because of that - which I think is outrageous age discrimination. Mind you he didn't get the silver medal because his results were a bit less spectacular than those of the winners, but rather they were so groundbreaking he couldn't be ignored, but because he was just over 40 they had to downgrade thr medal to a silver one (I guess in order to not be in conflict with the rules that the organization that awards the Fields medal has).

This is part of a general trend. As the world population ages, the number of people being able to achieve world-class performance later in life increases. One can see this spectacularly in sports, where older and older people win medals (for example: https://www.npr.org/2022/02/12/1080338798/older-athletes-bre... )

The Fields committee would probably do good updating their statutes, in order to not be so out of step with the times...