If that happens, the Zener AND the Arduino might be destroyed, possibly along with the 12V power supply.
If ESD is a problem, use a relay or optocoupler to electrically isolate the Arduino from the higher power segment of the system.
If that happens, the Zener AND the Arduino might be destroyed, possibly along with the 12V power supply.
If ESD is a problem, use a relay or optocoupler to electrically isolate the Arduino from the higher power segment of the system.