By adding a 15 V Zener diode and a resistor across the MOSFET which dims the LEDs, ... A transistor is also wired up, switching a 2.2 K resistor in parallel with the LEDs.

Both parallel and in-series connections provide zener-diode-voltage measurement at two current values. In some cases, I ZEN values may not fit the equation I ZEN −I ZENMIN <I ZEN <I ZEN −I ZENMAX, and ...

I certainly agree with you that a Zener diode could be used in the typical Zener regulator circuit, but it would be slightly more helpful to point to his mistake. In his example Vin=5V, Vout=3.3V ...

The regulator 78xxr, U1 utilizes the action of zener diode ZD1 which is in parallel with the potentiometer, R1. The tuning action of R1 produces a variable regulator output. The output voltage is ...