[2] Early in Emperor Wenzong's Taihe era (827–835), Zheng Su was recalled to the capital Chang'an to serve as a supervisory official at one of the ministries under the executive bureau (尚書省, Shangshu Sheng).
After Li Yong was subsequently created crown prince, Zheng was given an additional title as imperial attendant (給事中, Jishizhong).
[2] Early in Emperor Wenzong's Kaicheng era (836–840), Zheng was sent out of Chang'an to serve as the governor (觀察使, Guanchashi) of Shanguo Circuit (陝虢, headquartered in modern Sanmenxia, Henan).
[2] He subsequently served as the military governor of Shannan East Circuit (山南東道, headquartered in modern Xiangfan, Hubei).
[3] In 845, he was recalled to serve as acting You Pushe (右僕射), one of the heads of the executive bureau, and chancellor de facto with the designation Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事).