piezo analysis (oscilloscope)

a direct hit on a piezo
analog audio signal from -25V to +25V
during 2.5ms

i need to filter this signal for the adc of my mc.
schematic from my friend mamalala
200nf | 10k - 150k | 5.1 zener diode

using the schematic of this project
channel 1: adding a diode to avoid negative volts
channel 2: without a diode (like the original schematic)

using 1M
4.3 peak
30ms to return to 0V

102K
5ms to return to 0V

30K
2.5ms to return to 0V