The new circuit is an improved version of the previous one!

I think this is supposed to demonstrate us that this new circuit has a lot better voltage regulation compared to the previous circuit!

To find Vo, which is the voltage drop across RLoad, I'm firstly replacing the zener by a voltage source in series with a resistor (100 Ω).

Then I tried to write an equation for that green closed loop:

Vbe + Ie*RLoad = Vz + Iz*Rz

But I have not enough data to find Ve = Vo.

Then I tried to write another equation for the right side of the circuit starting in Vin all way down to GND:

Vin = Vce + Ie*RLoad

But I still have not enough data! I still have 3 unknowns and only 2 equations! And the transistor currents relations for the active zone are not taking me anywhere too, I guess!

A small push would be appreciated!