I think Zhang batters him. Dubois has had a resurgence of late, and I've done a bit of a U-turn on him, but I still think stylistically Zhang has the measure of him and would land his power shots often enough to get the stoppage.
If Dubois manages to survive until the moment when Zhang can no longer follow the rhythm, Dubois could knock him out, but he would have to constantly watch his defense...
Dubois is too hittable. Zhang by KO. I give Dubois much more chances against Parker than against Zhang
