just my experience... I did try using a Zener as a threshold sensor for 28V motor-drive system but it took longer (ie the DC-link crept up to higher potential then we wanted it to chop at) and it is un-controlled
comparator, Gatedrive, IGBT,Dump resistor and freewheel works, has worked and continues to work as expected.
Not saying a Zener can't be used but when do deal with real amps (ie a couple of hunded for starters not a couple on one's) its not as simple