Japanese second seed Naomi Osaka extended her winning streak to a 23rd match as she moved into the Miami Open quarter-finals for the first time.
Osaka, whose unbeaten run includes claiming the US Open and Australian Open titles, won 6-3 6-3 against Belgium's 16th seed Elise Mertens.
Australian world number one Ashleigh Barty also advanced by beating 14th seed Victoria Azarenka of Belarus.
Barty won 6-1 1-6 6-2 in a gripping contest with the 2020 US Open finalist.
Barty, playing in an overseas tournament for the first time in more than a year because of the coronavirus pandemic, continues her title defence against Belarusian seventh seed Aryna Sabalenka.