Li Sisong. Zhang Zeyu is a third-generation trainee of TF. He participated in the third season of "Music Master Class" in 2017. In the program, Zhang Zeyu's teacher was Li Sisong. The teacher wanted to teach Zhang Zeyu how to write songs and convey more love and emotion. Li Sisong, the twin brother of Li Weisong, was born in Singapore on July 24, 1966. He is a music composer and producer. He has written songs and produced albums for many well-known artists, such as the 1994 composition "I Wait Until the Flowers Wither" for Jacky Cheung.