Jankovic, the No. 8 seed, roared past Carla Suarez Navarro 6-0, 6-0 in 59 minutes. Jankovic won two-thirds of the points in the match. Suarez Navarro had three break chances but Jankovic fought them all off.
Radwanska, seeded third, took out Polona Hercog 6-0, 6-2 by going 6-of-8 in break opportunities. Radwanska claimed 60 percent of the points off Hercog's serve.
No. 1-ranked Serena Williams overcame a pair of breaks in defeating Maria Kirilenko 7-5, 7-5. Williams dropped serve once in each set but finished off both her break chances in the first set and was 3-of-5 in those situations in the second.
Williams, 70-4 on the year, improved to 8-0 in her career versus Kirilenko, who won only one set -- the first set of a French Open match in 2004 in their first meeting -- in the series.
No. 6-seeded Caroline Wozniacki is 3-0 all-time versus Sloane Stephens after her 6-3, 6-1 win Thursday and seventh-seeded Angelique Kerber beat No. 10-seed Roberta Vinci 6-2, 6-4. Also, Lucie Safarova edged Andrea Petkovic 6-4, 6-7 (4-7), 7-6 (7-2) in a match that took nearly 3 hours.
Williams goes against Wozniacki and Radwanska takes on Kerber in one of the draw's quarterfinals Friday. Jankovic is paired against Safarova while fourth-seeded Li Na plays No. 9-seeded Petra Kvitova in another quarterfinal.