Does this circuit do anything?
The circuit diagram editor (CircuitLab) built into the site is also a simulator.  I'm going to use that simulator to see what your circuit does.

Here's what your circuit looks like when drawn in CircuitLab:







simulate this circuit &ndash; Schematic created using CircuitLab

That circuit gives a pretty much linear voltage to the load:



The voltage over the load pretty much just follows the source voltage.  It is scaled a bit, and there's a small range at the very start where the voltage across the load stays at zero because the source voltage isn't high enough to make any of the diodes conduct.

All of your diodes are in the normal, forward biased condition.  That means that the Zener voltage doesn't come into play at all.  The diodes all have about 0.7 volts across them.

If I flip all of your diodes into the reverse biased condition, then it would look like this:







simulate this circuit

That gives you a voltage plot like this:



That's more interesting, but probably not what you expected.  The "knee" is at 150V, which is the sum of the Zener voltage for D2 and D4.  Only those two are actually doing anything.

D1 is effectively short circuited by R1.

D2 and D3 are effectively in parallel, so you only get the Zener voltage of a single diode - they act like a single diode.

Just to make it clear, here's how Zener diodes work:


Forward bias, normal diode:








simulate this circuit

That circuit produces this voltage plot:



Notice the voltage across the bottom is the source voltage, while the voltage up and down is the voltage across the diode.  It "snaps over" at around 0.7 volts.  The rated Zener voltage of the diode doesn't come into play.


Reverse bias, Zener diode








simulate this circuit

That circuit produces this voltage plot:



Again, source voltage along the bottom and diode voltage up and down.

Notice that it "snaps over" at about 5.1V (the rated Zener voltage of the diode.) That's the typical Zener action, and it only occurs when the diode is reverse biased.  A normal diode won't conduct at all when reverse biased.  A Zener diode doesn't conduct in reverse bias, either - until the reverse bias voltage exceeds the Zener limit for that diode.

Now, for comparison, here's a simple version of your circuit:







simulate this circuit

Because the order of the diode and the load are reversed, we get a different looking plot.  



The voltage at the load starts at zero because the Zener diode isn't conducting.  Once the source voltage reaches 5.1V, the diode starts conducting and the voltage across the load begins to go up.  It starts at zero, and follows the source voltage.  The voltage across the load is: \$V_{source} - 5.1V\$

I hope that (long) explanation helps you understand Zener diodes a little better.



When tackling a new subject, it is usually better to start with a simple example and work up rather than throw together something complicated and try to work down to the simple things.