Well, I should have googled first, but here's a link to an article about zaps becoming popular in the early 1970, perhaps originated by the Gay Activists Alliance (GAA).

By the time I came into the activist scene in 1990, the term "zap" was simply taken for granted, contrasted against "action" as a more organized and planned form of protest.

https://www.nationalgeographic.com/history/article/zapping-the-boisterous-protest-tactic-that-ignited-early-lgbtq-activism