I tried this last night after reading these post and i was not able to get any drops from electrified zombies using regular weapons. Though I only tried it for the first 4 rounds. But in the later rounds, I got the scavenger, upgraded it, made Romero go away and he dropped off the Wunderwaffe. So i pissed Romero off when he came back and got some electrified zombies. Lo and behold 2 max ammos drop off. So yeah it definitely works.