The issue is all about zener diode clipping circuits. I have failed to comprehend how the negative half is clipped at the cathode of the zener......
I am afraid I might end up deranged here unless somebody comes in and sort of 'assassinate' my puzzle. here outgoes the mystery of zener diode clipping circuits with the one connected series opposing being the notorious one. I have decided not to tolerate the claim that the negative half cycles of the AC waveform get clipped at the zener's cathode, the overtaking question being why clipping instead of forward-biasing. may someone 'break every chain' as to how this happens to do, otherwise I wont have ends meet here. A little knowledge is a dangerous thing- I don't want to be dangerous!
Your description of your problem is a bit rambling. Anyway, here are some explanations of how a Zener diode works including some YouTube videos.
If you are still unable to understand how a Zener works, I suggest you find a competent electrical engineer to help you do what you are trying to do before you become "dangerous."
William (Bill) L. Mostia, Jr. PE
ISA Fellow, FS Eng. (TUV Rheinland)
WLM Engineering Co.