Mikes right, the 2nd one would fry the zener or transistor, but on this circuit, it worked repeatedly, dropping the relays at 12.52 volts, the zener measured 11.95 volts. I have a 50,000 µf, 40 volt capacitor and I would charge it, trip the relay on and measure the voltage when the relay opened, 12.52 volts, tried it with 2 different relays, and got the same opening voltage. One relay was 86.3 Ω and the other was 378.3 Ω. I used this exact circuit, except I didn't put the protective diode across the relay and shorted across the N. O. contact with a piece of wire.
Kinarfi