American Heritage Dictionary of Idioms

attention to, concentrate or focus on, as in We've got to zero in on the exact combination of ingredients, or The whole class zeroed in on the new assignment. This usage transfers aiming a firearm to directing one's attention. [Mid-1900s] 3. Converge on, close in on, as in The children zeroed in on the electric train display. [Mid-1900s]

zone out

Stop paying attention, dissociate oneself from a situation, as in When Felicia starts talking about her ailments and her friends' ailments, I totally zone out. This idiom also occurs in the passive as be zoned out and originally alluded to narcotic intoxication and then was broadened to other kinds of dissociation. For a near synonym, see TUNE OUT, def. 2. [Slang; second half of

1900s]

zoo

hand. see IT'S A ZOO.

zoom in on

1. Obtain a closeup view of the subject with a camera, as in The TV people zoomed in on the Olympic gold medalist. [Mid-1900s] 2. Focus on, examine closely, as in The moderator got the panelists to zoom in on the health-care issue. [Second half of 1900s]