Plenty of guys have taken max down: Bermudez, Fili, Conor, Old Frankie, ortega, Volk.....
No one in recent years have had success holding him down. That said, KZ is a very good all around grappler, and the guy is a huge FW (he weighed 170lbs eight hours after weighing in at 145lbs...) he'd be very heavy on top.
If KZ could actually establish top position on Max, i think he'd have a pretty big advantage. I just don't know if he could. I do think that mixing in his grappling would be essential, though, even if he didn't get the takedowns. Historically Max's output has been lower against guys who kept him honest with the takedown threats, and that might help KZ find his chances on the feet to hurt max.