Katie Boulter and Harriet Dart both won at the Nottingham Open to set up an all-British quarter-final.
British number one Boulter, 26, overcame Ukrainian lucky loser Daria Snigur 7-5 6-3 in a tricky encounter at the grass-court event.
Dart, ranked 143rd in the world, then beat Ukraine's Anhelina Kalinina 6-0 7-5 to reach the last eight.
Andy Murray is in last-16 action against France's Hugo Grenier later on Thursday.
Boulter holds the top British women's ranking for the first time in her career after reaching the semi-finals of the Surbiton Trophy last week and jumping ahead of Emma Raducanu, who has been hampered by injuries.