The Czech Republic's Zakopalova had little trouble besting Poland's Katarzyna Piter on the clay courts of Jockey Club Brasileiro, recording a 6-4, 6-0 triumph.
She'll next face crowd favorite Pereira, who advanced to the semis with a 6-4, 6-4 decision over Romanian qualifier Irina-Camelia Begu.
Saturday's other semifinal match was set when Italian qualifier Nastassja Burnett surprised third-seeded Argentine Paula Ormaechea 5-7, 6-2, 7-5, and No. 5 Kurumi Nara of Japan topped Spaniard Lourdes Dominguez Lino 7-6 (7-5), 2-0, retired.
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