Nadal beat Paul-Henri Mathieu 6-4, 6-2, 6-2, and next faces sixth-seeded Robin Soderling, the Swede who beat him in the fourth round at the French Open last year. Nadal beat Soderling in last month's French Open final.
Soderling, who hadn't dropped a set until Monday, needed five sets to beat No. 9 David Ferrer 6-2, 5-7, 6-2, 3-6, 7-5 to make the quarters for the first time.
Djokovic beat 2002 champion Lleyton Hewitt 7-5, 6-4, 3-6, 6-4 to reach the quarterfinals for the second year in a row.
Murray swept past American Sam Querrey 7-5, 6-3, 6-4 to reach the final eight for the third consecutive year.
Murray, seeking to become the first British player to win the men's singles title since Fred Perry in 1936, will next meet 10th-seeded Frenchman Jo-Wilfried Tsonga.
Vera Zvonareva advanced when fourth-seeded Jelena Jankovic retired with a back injury while trailing 6-1, 3-0. The Russian will next face Clijsters.
Third-seeded Caroline Wozniacki lost 6-2, 6-0 to unseeded Czech Petra Kvitova.
Also making the quarters were No. 9 Li Na of China, Tsvetana Pironkova of Bulgaria and qualifier Kaia Kanepi of Estonia.