Weird–apparently the now widely used phrase “in the zone” is a reference to The Twilight Zone tv series.
Quote Investigator: During 1973 and 1974 the top tennis player Arthur Ashe kept an audio diary, and in 1975 he published “Arthur Ashe: Portrait in Motion” primarily based on his daily recordings. The earliest evidence of the phrase located by QI appeared in a diary entry dated February 22, 1974 in which he discussed a match with another prominent player named Bjorn Borg. Emphasis added to excerpts by QI: 1
I thought I was playing unconscious, but Borg beat me 6-4, 7-6 tonight, and he is in what we call the zone. (That comes originally from “twilight zone” and translates, more or less, into “another world.”) The kid has no concept of what he is doing out there—he is just swinging away and the balls are dropping in. He has no respect for anybody. Hell, he should win the whole tournament.
From tennis, the “in the zone” phrase spread to other sports and then to the larger culture.