OSAKA, Japan (AP) - Sixth-seeded Madison Keys reached her fourth WTA quarterfinal of the season Thursday by beating China's Shuai Zhang 6-3, 6-0 in the second round of the Japan Open. The 18-year-old American won nine successive games to wrap up the match in just 51 minutes. Keys lost just three points in the second set. Ninth-seeded Kristina Mladenovic of France faltered after winning a 67-minute first set, losing 6-7 (5), 6-2, 6-0 to Jie Zheng of China. Jie will play Keys on Friday for a place in the semifinals. Misaki Doi also reached the quarters by beating fellow Japanese player Kimiko Date-Krumm 7-6 (3), 6-4. Doi will face American Samantha Stosur, who at No. 3 is the highest seeded player still in the tournament.