According to producer Zhenyu Li, there was much discussion among the team when creating the game's characters, often starting with the question, "What have players not seen before?" For example, maid characters had been done several times by that point, prompting the devs to try to brainstorm more elements that could keep them interesting. Their solution for the maid designs was to add tropes commonly seen in horror movies to create a new aesthetic, thus resulting in the designs for the Victoria Housekeeping Co. faction.

To promote the release of the game, HoYoverse collaborated with the YouTube channel Lofi Girl to release a Zenless Zone Zero-themed video featuring the character Belle on the HoYoFair YouTube channel. Similar to Lofi Girl's content, the video features lo-fi remixes of select songs from the game's soundtrack.

Jane Doe's name has two different references in it. The first and most obvious one is a reference to the term "Jane Doe", a placeholder name used in cases where a female individual's real name is either unknown or intentionally concealed (ironically, her Spoiler:New Eridu Public Security (NEPS) Consultant Card implies that her name really is Jane Doe rather than an alias). The second reference is found in her last name "Doe", which is what female fancy mice (domesticated breeds of common house mice) are often referred to as. Both of these references are fitting for Jane's character as she is a mouse Thiren with prominent ears and a tail, and because Spoiler:she works for NEPS as a consultant, specializing in criminal psychology and infiltrating dangerous groups.

On May 13, 2024, the Angels of Delusion faction (tentatively referred to as "Virtual Idols") was leaked by an unknown party through illegal means of obtaining development data, including character design concept drafts. Rather than cover it up, however, the official Zenless Zone Zero bilibili account opted to reveal the group in a blog post and explain details about it. The idea first came about from students on the production team who had a fondness for idol culture and how they believe it can give people strength, giving descriptions on the individual members: "a lead singer who wants to ignite everyone's enthusiasm with her singing, an artist who is born to be the focus of the stage, and a creator with delicate emotions and great talent." They also expressed interest in making real virtual idols based on the group once the designs were finalized, and creating related projects such as character songs around them. In a YouTube video uploaded on April 7, 2025, it was revealed that the faction would be coming to the game during Version 2.0.

To promote the release of Zenless Zone Zero, publisher HoYoverse collaborated with several graffiti artists to create graffiti based on the game across nineteen different cities in Indonesia.