Danielle Collins scripted a fine comeback win to battle past fellow American Katie Volynets 4-6, 7-6(3), 6-0 to secure a place in the Austin Open quarterfinals.
Also in this quarter are 2021 US Open champion Emma Raducanu, No.12 Liudmila Samsonova, No.13 Beatriz Haddad Maia, No.19 Madison Keys, No.20 Magda Linette, No.30 Leylah Fernandez and Danielle Collins.
In the pre-quarters, Swiatek will take on last season's Wimbledon champion Elena Rybakina of Kazakhstan, who defeated the previous year's runners-up Danielle Collins 6-2, 5-7, 6-2 in their third-round match-up
Playing just their third tournament together as a team, Zhang and Mertens needed one hour and 42 minutes to successfully fend off a comeback by the Americans 6-2, 3-6, 6-3.