Capacitor in parallel with relay coil backfires on contacts
If you happen to apply the power at the positive or negative peak of the mains (325 volts), for an instant more than 300V appears across R2||R3. Your series resistor R1 should probably be in series with the C2 to the mains and C1 connected across the bridge output and no diode D6, unless I'm really misunderstanding what you are trying to do. R1 needs to be an overload-resistant type. 

C1 has very low value for smoothing 100Hz to relay coils, and the series 100 ohms means it charges quickly but can't supply much current - maybe your D6 is actually the other way around. I would think something in the 100-470uF would be more like it for C1. 

You'll want to calculate C1 ripple (and keep that low enough the zener regulates, assuming that voltage is used for something).