3.3v Zener Diode Shunt Voltage Regulator giving a 4.3v output
You have a fundamental misconception about how a shunt regulator works.

The key idea is that you size the series resistance for the peak load current by itself. Then, whenever the load does not actually draw that peak current, the Zener diode "shunts" the excess current to ground. In other words, when the load current goes up, the Zener current goes down, and vice-versa. The Zener dissipates the maximum power when the load is drawing its minimum current.