Pin limit is VCC+0.5volt and GND-0.5volt.
That circuit useless, because it does not clip the negative peak to <=0.5volt.
What if the Arduino is off. Then clipping should be +0.5volt and -0.5volt.
Zeners are generally useless for pin protection.
Two schottky diodes is a better solution.
One from pin to VCC (cathode to VCC), and one from pin to ground (cathode to pin).
As said, not needed for low energy piezos.
Leo..