That's a very good matchup Tbh.
Islam had very good kicks, and very good boxing defense.
Also, No-CuttingWeigth-Islam probably is a monster without cardio problems. (People usually says he slow down too much in 2nd round)
Belal in other hand is the best wrestler islam has ever faced (in cage), he have really good boxing and top control... He's the classic wrestler-boxer.
Probably islam is better at Long-Range, while Belal get the best in Mid-Range.
The problem for islam is, Belal is the bigger guy here.
I think Belal have a better control, but Islam's ground game presents a lot more danger.
Belal is bigger and heavier, but I think islam just have more tools, to land/reverse takedowns and to submit on the ground.
I think it would be a truly entertaining figth. Belal is famous to bring snoozefests too us, but he's a pressure fighter, also islam certainly would bring the action here, both in feet or in the ground.