Max. Someone with the combo of unusual power and years of boxing experience is the absolute worst matchup for Francis. Francis's best shot is against people who wouldn't crack his chin for awhile. I have no doubt Max could.
With no disrespect intended for Francis Ngannou (he has very little boxing experience), but I would be surprised to see him still involved in the fight in the second round. I will go with Max Baer by KO 01.