[Amps] switchable zener cathode bias

[Steve Flood]

Considering the common zener bias circuit (with the 2n3055 and resistor), what precautions should be taken if I wanted two different zeners (and associated bias voltages) selected by a switch or relay?   Is there a danger in the moment when the switch/relay throw is transferrring from one pole to the other and neither zener is in the circuit?   Likewise, if I used a make-before-break setup, can the two zeners be in parallel for a moment without causing trouble?

Thanks,
Steve KK7UV