Identify the Maximum Voltage that can be applied across Zener, MOSFET and Transistor
Zeners are designed to operate in breakdown. Thus hotspots must be avoided.

MOSFETS and Bipolars are not designed to operating in breakdown, tho I've seen schematics using the 2N2169 NPN (Jim Williams of LTC uses this device) in a sub-nanosecond pulse generator, where the avalanche performance (a breakdown mode) produces the fast onset of charge movement and hence the fast edge.

I suspect your performance with such a circuit will strongly depend on who manufactured the transistor, given the avalanche speed is not spec'd in datasheets.