WOMEN'S tennis in China celebrated another victory on Sunday as Sun Tiantian and her mixed doubles partner Nenad Zimonjic of Serbia won the mixed doubles Australian Open title. The win is Sun's first Grand Slam title. Zimonjic's usual partner, Katarina Srebotnik of Slovenia, chose not to participate in the mixed doubles tournament. When Zimonjic came looking for a partner, Sun agreed to join him. "I did not have any pressure. Nenad told me before the match just to play [for] fun, so I did," said Sun, 26, after winning the semifinals last Friday. Sun and compatriot Li Ting won the women's doubles gold at the Athens Games in 2004.