I'd be shocked if Zidane manages them
Judging by his managerial career it doesn't seem like he's that desperate to be a full-time manager and isn't exactly going from club to club. He also won a lot in a very short space of time during the time he did manage, so he has never tarnished himself.
Considering he doesn't seem to be that desperate to be a full-time manager year in and year out, then I cannot see why he would choose a team that is clearly inferior to other teams in England and it's a real uphill battle. Unless he wants a mega challenge, who knows.
If he just wanted money, he could probably get a job in Saudi within a day of showing interest.
Maybe I'm completely misjudging him, but I just don't see how United at this moment are appealing to him. Inheriting a poor squad and team, a pretty toxic feeling around their club, as well as going up against far superior teams managed by Pep, Klopp etc.
Unless he's bang up for an incredible task on his hands, I don't see why he takes the job.