Beginning in April 2023, prior to the EP's announcement, Jihyo performed an unreleased track, "Nightmare", on Twice's Ready to Be World Tour, leading to speculation that she would soon make a full solo debut.

[2][3] On June 5, 2023, Twice hinted at a mysterious project set to release in August with the text "Killin' Me Good" inscribed on the teaser image through their social media pages.

[5] Another visualizer of Jihyo with her mouth covered with moving images was teased on June 26, 2023, officially revealing her first EP titled Zone led by the lead track "Killin' Me Good".

[11][12] On July 31, 2023, JYP Entertainment revealed the EP's tracklist and released a third spoiler of "Killin' Me Good" with Jihyo humming the tune of the song at a home recording studio.

[17] The album opens with the lead single "Killin' Me Good", written by Twice's longtime collaborators, Park Jin-young for the lyrics, Melanie Fontana and Lindgren for composition.

[25] Track four, "Wishing On You," is an R&B song characterized by a dreamy melody and "captivating vocals", with lyrics that express "the excitement and thrill" of thinking about someone all night long.

[26] The fifth track, "Don't Wanna Go Back,” a duet with South Korean singer Heize, is an "emotional" ballad[23] and R&B song driven by an acoustic guitar and bass.

[28] It broke the record for the highest initial sales volume for a extended play released by a K-pop female soloist in Hanteo chart history.