The ever-willing qualifier Duckworth, still going strong at 33 despite an injury list that would have sunk lesser athletes, enjoyed his best victory of the year, knocking out last year's finalist Gabriel Diallo 7-6 (7-3) 6-7 (3-7) 6-4 in the last-16 of the Almaty Open in his fourth match in five days.
Meanwhile, former Australian No.1 Tomljanovic will surge back into the WTA's top-100 next week after beating Turkey's Zeynep Sonmez 7-6 (8-6) 6-3 in straight sets in her last-16 contest on Wednesday, also her fourth win in five days at China's Ningbo Open.
Duckworth heads another strong contingent of Australians at the Kazakhstan event where he reached the final back in 2021, the year after compatriot John Millman had won there.
He's the first to make the quarter-finals with both Adam Walton and Aleksandar Vukic facing tough last-16 matches on Thursday.
Diallo, the 24-year-old Canadian who has moved up to No.35 in the world, represented a considerable scalp for Duckworth, who is down to No.138 in the rankings and hadn't reached the last-eight of any event since Los Cabos in Mexico in July.
But he served really well, staying unbroken all match, to set up a last-eight meeting with Flavio Cobolli, the rising Italian No.3 seed who defeated another Sydneysider Rinky Hijikata, a lucky loser, 6-4 7-5 on Wednesday.
Just like Duckworth, the 32-year-old Tomljanovic has appeared to thrive on a hectic schedule, winning her fourth match of the week in Ningbo on Wednesday even though she started terribly against Sonmez, going 5-0 down in the opening set and having to save a set point at 2-5 while rallying dramatically.
Tomljanovic, who's 104 in the world but is set to rise to at least 86 on the live rankings, then held toughest in a nervy second set where serve was broken five times in a row.
It will be Tomljanovic's third quarter-final of the season and her first at WTA 500 level or above since the 2022 US Open, where, famously, she beat Serena Williams on the way to the quarter-finals in what was to be the great champion's last match.
It's now set to get much harder for Tomljanovic, who'll next face either No.3 seed Elena Rybakina or Ukrainian Dayana Yastremska in the quarters.
