He founded ByteDance in 2012, developed the news aggregator Toutiao and the video sharing platform Douyin (internationally known as TikTok).

[12] This vision was not shared by most venture capitalists, and he failed to secure funding until Susquehanna International Group agreed to invest in the startup.

[13] He insisted that ByteDance's workplace productivity app Lark be targeted at the American, European and Japanese markets, rather than limiting the focus to China as originally proposed.

[14] Zhang's management style with ByteDance was modeled on US tech companies such as Google and included bimonthly town hall meetings and discouraging employees from calling him "boss" or "CEO", as is the Chinese convention.

In response, Zhang issued an apology, writing that the app was "incommensurate with socialist core values" and had a "weak" implementation of Xi Jinping Thought, and promised that ByteDance would "further deepen cooperation" with the ruling Chinese Communist Party to promote its policies better.

[12] In September 2020, the United States Department of Justice called Zhang a "mouthpiece" of the Chinese Communist Party in a legal filing.

[19] In May 2023, The New York Times reported that a former employee accused Zhang in a lawsuit of facilitating bribes to Lu Wei.