The 25-year-old Frenchman had already knocked out third seed Tomás Martín Etcheverry in the second round. Against Marozsán he saved three set points in the opening tie-break and two break points while serving for the match at 5-4. He saved all three break points he faced and won in one hour and 47 minutes.
“It was a great match. I had to stay focused during the entire match because it was really tough,” Jacquet said. “I am really happy about my performance today, my attitude and everything else. It was really strong and that’s why I won. I am really proud of myself.”
Jacquet has risen 25 places to No. 85 in the live rankings. He will face second seed Andrey Rublev or compatriot Hugo Gaston for a place in the final.
Top seed Daniil Medvedev reached the quarter-finals on Saturday by beating Valentin Royer 7-6(6), 6-3. China’s Buyunchaokete and Roman Safiullin also advanced.
Jacquet’s run from outside the top 100 seeds has been the story of the second week in Hangzhou. A first tour semi-final awaits after two straight-set wins over higher-ranked opposition.