AS we know Vz = Vo, that means we have the value of Vz.

For there we have to choose the zener diode with breakdown equal to Vz.

And after selecting the model number, you just have to check the minimum & maximm current ratings of that zener.

From there you’ll get your values of Iz max & min.

And also you have the maximum & minimum values of load current. So now let’s get the limits if Rs using the equations given below: