Did you attack first? If sois it possible for an magnezone to 1 shot an porygon z with volt switch? and im not talking about a crit.
That just happened to me in a battle but i have an hard time believing an neutral hitting volt switch can 1 shot porygon z while its not even a crit since porygon z is decently bulky and magnezones physicla attack isnt that high
252+ SpA Choice Specs Analytic Magnezone Volt Switch vs. 0 HP / 0 SpD Porygon-Z: 310-366 (99.6 - 117.6%) -- 93.8% chance to OHKO
Edit: even timid specs has a 43% chance to Ohko if it's analytic