Where else NOT SHOWN on the schematic is the ground connected ?
I can understand your concern or consternation. That would be all.
Another bit of help: The transistor is a general-purpose one. A 2N2222 or 2N3904 will work.
For the BZV55C5V1 is also a common 5.1 volt Zener of the 1N5338 type.
ETA: The resistor wattage: a 1/4 watt or even 1/10 watt would do fine.