Yes, "zap" suggests something quick, like lightning. Strangulation would not be a zapping.

I think people would use "zap" mostly if they were talking about video games, comic books, or electric fly-swatters. If it was something that happened in the news to a real person, they would not say "zap". Zap would mean electricity, or maybe magic, but not something like a gun or getting run over by a car. Also, you could get "zapped" but not killed - like if you got a small electric shock.

The word "zap" is slang. I can use this word informally to warn someone to avoid lightning. I don't want them to be struck so I might tell them not to be "zapped" by lightning. The "zap" is the conduction of electricity.