Yes, the zener diode is a simple voltage regulator. The PN2222 in my schematic is not adequate for a 1.5 amp relay, a better choice would be an FET like IRF510. R3 could then probably be eliminated. The IRF510 will not need a heat sink.
The 555 is more commonly used as a current sink for low duty cycle applications and as a source for high duty cycle applications because the minimum duty cycle without a diode is 50%