You are welcome.....Note that the zener diode in the circuit I sent is put there to save the opto coupler in the case that the coil voltage rings to a negative value.

Opto coupler LED's don't like to be reverse biased to very high of voltage. The zener takes care of that and simultaneously provides a clamp on how much voltage gets into the circuit if the coil voltage rings to a high positive value.
Hope that explains the Zener.
Mike Karas