[1][2]), courtesy name Zhengqiu (正求), was an official of the Chinese Tang dynasty, serving as a chancellor twice during the reign of Emperor Xizong.
It was said that he selected appropriate officials while overseeing the civil service, but that, as a result of refusing to bow to powerful individuals' wishes, was sent out of the capital to serve as the military governor of Hedong Circuit (河東, headquartered in modern Taiyuan, Shanxi) as well as the mayor of its capital Taiyuan Municipality.
[4] He was thus transferred to Lingnan East Circuit (嶺南東道, headquartered in modern Guangzhou, Guangdong) to serve as its military governor and the prefect of its capital Guang Prefecture (廣州).
[7] Zheng Congdang, who did not want to remain in Lingnan East longer, submitted repeated petitions, offering even to accept an honorary position at the eastern capital Luoyang.
[4] In 878, when Zheng was referred to at the minister of civil service affairs (吏部尚書, Lìbu Shangshu), he was made Zhongshu Shilang (中書侍郎), the deputy head of the legislative bureau, and given the designation Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事), making him a chancellor de facto.
[8] Back at Hedong, Zheng Congdang was described as apparently mild in disposition, but was full of strategies and decisive.
For example, the officer Zhang Yanqiu (張彥球), who was forced by his colleagues to participate in the mutiny that killed Kang Chuangui, was someone that Zheng comforted and entrusted with military commands.
Meanwhile, in 881, Li Keyong, claiming that he was coming to the imperial government's aid, requested that Zheng allow him transit through Hedong.
The chancellor in charge of the operations against Huang, Wang Duo, thus issued an edict in Emperor Xizong's name pardoning and summoning Li Keyong to the imperial cause, and further ordering Zheng not to interfere.
In 886, he was given the greater chancellor title of Shizhong (侍中, i.e., the head of the examination bureau), as well as Taifu (太傅).