Forget the typical current, what is worst case?
I am not seeing any particular shortage of 75V, half amp class bucks from the usual suspects (TI, Linear, Maxim if you really must), but if they are unsuitable for some reason then 60V is a very common upper limit for a buck converter (Telecoms loves its 48V rails) so I would probably do the zenner thing to get there or there about, then use a small buck converter.
if you assume say 1W worst case (200mA @5V) then with say 50V at the buck input you are looking at ~20mA on the input side, if we design to drop say 25V across a zenner then the zenner would be dissipating 0.5W.
Note that there is a small trap here, in that the series zenner will dissipate MORE power as the input voltage drops, because the buck will consume progressively more current.
24V, 1.5W zenner in series with the input and say a LMR16006YDDCT in a datasheet circuit would be my instinctive approach, make sure your minimum load pulls sufficient current thru the zenner at maximum input voltage to keep the voltage drop sufficient.
Regards, Dan.