Han, a wild-card entrant, ousted fifth-seeded Chang Kai-China 1-6, 6-2, 6-4 behind eight service breaks. She won 55 percent of the points on Chang's serve and Chang hurt her own chances with nine double faults.
Zhang needed just 63 minutes to dispatch No. 8-seeded Chanelle Scheepers 6-1, 6-0. Scheepers had seven double faults and won only 14 points on serve.
No. 3-seeded Akgul Amanmuradova was also defeated, losing 6-4, 6-3 to Mirza, who dropped serve just once in the win.
Camerin capped the day with a 6-4, 3-6, 6-4 triumph over seventh-seeded Alberta Brianti. Camerin won the first three games of the match but needed a break in the 10th game of the final set to secure the win.
Also, Wednesday Alla Kudryavtseva got past Ekaterina Ivanova 6-4, 3-6, 6-2.
Zhang will go against Mirza in the quarterfinals. Wednesday's other second-round winners will have to wait until Thursday's play before learning their quarterfinal pairings.