How old was Zhang Depei when he practiced tennis?

Zhang Depei's father, Zhang Hongsheng, immigrated to the United States from Taiwan Province Province on 1966. He is a chemistry researcher and likes tennis very much. He has two sons. When Zhang was nine or six years old, he began to teach them to play tennis.

1984, 12-year-old Zhang Depei won the American youth hard court tennis singles championship. 1987, 15 years old, national junior tennis champion. 1988, 16 years old officially entered professional tennis. In September of the same year, he won the National Open in San Francisco, and his professional ranking rose from 163 to 30, becoming the best newcomer in professional tennis that year.

1988, Zhang Depei was given a wild card by the French Tennis Organizing Committee to accumulate experience on the court in Roland Galos.