China's Zheng Qinwen reached the last eight of the Miami Open on Monday, aiming for her sixth career title. (Photo credit to the official Weibo of the WTA)MIAMI, March 24 (Xinhua) -- China's Zheng Qinwen reached the last eight of the Miami Open with a 6-2, 7-6(3) victory over American Ashlyn Krueger on Monday.Ninth-seed Zheng hit five aces and won 81 percent of her first-serve points as she took the match in an hour and 29 minutes.Krueger struggled for rhythm on serve, committing four double faults, while winning only 27% of total points on return.Zheng's quarterfinal opponent in the WTA 1000 event will be top seed and world No. 1 Aryna Sabalenka, who advanced by beating defending champion Danielle Collins 6-4, 6-4 in their fourth round duel.Zheng, the reigning Olympic women's singles champion, is aiming for her sixth career title.