Zener doesn't seem to be working
KVL rules here. The zener branch (R1 and D1) will be at the same voltage as the capacitor branch (D2, R2, and C1), which will be 9V.

If you want the zener to limit the cap voltage, you need to move D2 to the midpoint junction of R1 and D1.







simulate this circuit &ndash; Schematic created using CircuitLab

Don't forget that D2 will eat a few hundred millivolts, meaning your cap voltage could end up as 1.6V or so.

Once you get the basic idea of how the zener clamp works, you can start playing around with the resistor values (hint: is R2 really necessary?) and see how the performance is impacted.