Marin Cilic and Sam Querrey ensured there will be three former champions in the quarter-finals with victories on day four of the Aegon Championships.
Fourth seed Cilic beat 19-year-old American Stefan Kozlov 6-0 6-4.
"Serving well is they key on grass and I did that really well again today," said the 2012 champion, who is yet to face a break point.
American Querrey, the 2010 winner, beat Jordan Thompson - conqueror of Andy Murray - 7-5 (7-3) 3-6 6-3.
Bulgaria's Grigor Dimitrov, champion in 2014, is already through to the last eight, where he will face Russia's Daniil Medvedev.