Wozniacki, a two-time defending champion in the event, dispatched Pauline Parmentier 6-2, 6-1 in 67 minutes. She took nearly three-quarters of the points on serve and didn't see a break point in the match.
Three of the top four seeds in the tournament were on Thursday's schedule and only one failed to advance. Bojana Jovanovski eliminated fourth-seeded Monica Niculescu 6-7 (6-8), 6-4, 6-1 in a match that lasted more than 2 1/2 hours. Jovanovski dropped her serve twice but saved all five of the break points she faced after the first set.
Wozniacki draws Alize Cornet in Friday's quarterfinals while Jovanovski goes against Petra Martic also in the half of the bracket. Kerber is to play sixth-seeded Mona Barthel and Jankovic meets No. 5-seeded Kaia Kanepi in the other quarterfinals.