Kerber, the top seed at the WTA International event in Mexico, was too good for Karolina Muchova 6-3 6-4 in the second round.
The German two-time runner-up powered into the quarter-finals, where Kirsten Flipkens awaits.
Muguruza’s title defence remains alive after the Spanish second seed overcame Margarita Gasparyan 6-3 6-7 (1-7) 6-2.
Awaiting her in the last eight is Kristina Mladenovic, who eased past 39-year-old lucky loser Greta Arn 6-0 6-2.
Also progressing in Monterrey on Thursday was two-time grand slam champion Victoria Azarenka, the Belarusian beating Zarina Diyas 6-3 6-2.
At the Charleston Open, 2011 champion Wozniacki battled past Mihaela Buzarnescu 6-4 3-6 6-3 in the third round.
Wozniacki will meet Maria Sakkari in the quarters after the Greek 15th seed beat defending champion Kiki Bertens 7-6 (10-8) 6-3.
In the top half of the draw, Sloane Stephens and Madison Keys will face off in a blockbuster all-American quarter-final.
Stephens, the 2016 champion, edged Ajla Tomljanovic 4-6 6-4 6-4, while Keys was too strong for Jelena Ostapenko 7-5 6-2 in a clash between two former runners-up.
Petra Martic and Belinda Bencic will meet, while Danielle Collins faces Monica Puig.
Puig is the only unseeded player remaining in the draw after the Puerto Rican upset Aryna Sabalenka 6-2 7-5.
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