Tyson would bob and weave his way to body shots on Shaq.
Shaq probably hits pretty damn hard, but likely telegraphs every single punch. A regular breh would get washed but Mike would avoid every single hit.
Now if Shaq could get him on the ground????? That's more of a toss up. Being really tall/long arms/long legs can be problematic when grappling. It can give you leverage but also make you easier to attack.