1389, Li Chenggui deposed Chang Wang and established Gongrang Wang. Zheng took part in this matter, and he was named a hero for his achievements. Zheng Mengzhou and others supported Gongrang Wang and wanted to suppress the forces. Zheng was an adjutant, so he was impeached and exiled again in 139 1 year. 1392 was released, and in April of the same year, Li Chenggui fell off his horse and was injured while hunting. During his illness, Zheng Mengzhou and others impeached Zheng in the name of "impure family background and untrue family background" and made him exiled again. After Li Fangyuan assassinated Zheng Mengzhou, Zheng was released. On July 17 of the same year, Zheng Li became king and established the Korean dynasty. Power is concentrated in Zheng's hands, and his power is even superior to that of the great ancestor of North Korea. The Korean dynasty appointed him as assistant minister in charge of affairs, judge of capital appraisal, judge of Cao affairs in the Ministry of Household Affairs, judge of Shang Rui affairs, judge of Pumen Pavilion, judge of Spring and Autumn Period, judge of Yixing in the Three Armies, etc. He has held or concurrently held an important position in the court. At the same time, it is recognized as the first-class hero of the founding of the country.
After the Korean dynasty moved its capital to Seoul, the positions and titles of palaces and ancestral temples, as well as the titles of various doors in Seoul, were drawn up by Zheng. At the same time, he compiled Korean classics and contributed to the legal foundation of the Korean dynasty. His book Miscellanies of Buddhism laid a theoretical foundation for the policy of worshipping Confucianism and restraining Buddhism in the late Korean dynasty.
Militarily, Zheng reformed the military system. At the end of the Koryo dynasty, there was privatization, that is, powerful people owned private armies. Zheng deposed the private soldiers and nationalized them. At the same time, he added some array laws to enhance the national defense strength of the Korean dynasty.
Zheng had a great influence in the imperial court. Han Taizu conferred the title of Prince Li, the eldest son of Yi 'an, and appointed Zheng as the head of the Prince. This caused the dissatisfaction of Mao's fifth son. So he launched a mutiny in 1398, killed and seized the political power, which is known as the First Prince's Rebellion in history. Zheng was killed in this coup.