I'm not going to compare any player, especially with players like Zidane but the fact about Bellingham is he is so young and he joined Real Madrid when he is 19y old, in the other hand Real Madrid is a team where you can have good coaches to improve your skills, that's why I think a player like Bellingham can have the chance to even become better than Zidane if everything goes well for this players because he got enough potential for it.
Anyway, Zidane is a legend. And I personally wouldn't to brave compare Bellingham with Zidane either, because Zidane has proven to be a genius player, his achievements also look very great. But yes I agree Bellingham can have the chance to even better than Zidane, if everything goes smoothly without injury hindrance of course. Because if the injury will hinder the progress of his career, but right now Bellingham is at a great club, hopefully he can quickly adaptation and develop there.