It is not known when Zhao Yanzhao was born, but it is known that his family was originally from Gan Prefecture (甘州, roughly modern Zhangye, Gansu).
He later served as an imperial censor during the reign of Wu Zetian and authored a 10-volume work on the notable people of the Hexi Corridor, the region he was from.
In 709, during the reign of Wu Zetian's son Emperor Zhongzong, Zhao Yanzhao was promoted to be Zhongshu Shilang (中書侍郎), the deputy head of the legislative bureau of government (中書省) and given the designation Tong Zhongshu Menxia Pingzhangshi (同中書門下平章事), making him a chancellor de facto.
In 710, Emperor Zhongzong was set to marry Princess Jincheng, the daughter of his nephew Li Shouli the Prince of Yong, to Tufan's king Me Agtsom.
Shortly after Emperor Ruizong took the throne, Zhao was demoted to be the prefect of Jiang Prefecture (絳州, part of modern Yuncheng, Shanxi), but was almost immediately recalled to again serve as Zhongshu Shilang and chancellor.
He was subsequently recalled to serve as the deputy minister of civil service affairs (吏部侍郎, Libu Shilang), and later the chief imperial censor (御史大夫, Yushi Daifu).
Two of the officials involved in Emperor Xuanzong's purge who served chancellors, Guo Yuanzhen and Zhang Shuo, were friendly with Zhao Yanzhao, and they claimed that he was part of the plot as well.
These former chancellors were all demoted, with Zhao reduced to being the secretary general of Jiang Prefecture (江州, roughly modern Jiujiang, Jiangxi).