This circuit is a death trap - you should never be connecting directly to the mains live or neutral like this - either live or neutral wire can have lethal voltages on it and should be treated with equal respect.
Secondly most single resistors are not rated for mains voltages (remember during lightning strikes and other transient events you will see kilovolt level voltage spikes on the mains, leading to flashover on a low-voltage resistor, starting a fire and breaking the isolation barrier. Special high voltage resistors are used in these situations.
Thirdly Schottky diodes have excessive reverse leakage for high voltage use, so if the zener fails you'll risk thermal runaway of the Schottky and possible failure - again risking starting a fire.
Unless you understand the risks and regulations of circuitry directly connected to the mains, do not do it...
When you see mains equipment with things like a UL (Underwriters Laboratories) logo (*), it means the equipment has been thoroughly tested for many failure modes and doesn't pose a risk of electrocution or fire in those events.
Get a small (UL listed!) mains transformer and use the secondary voltage for your sensing - this is the safe and legal. Don't forget a fuse (the fourth error with that circuit BTW).
(*) cheap rubbish from China excepted - this stuff is often unsafe and to be avoided.