Sinner is in the semi-finals at the prestigious ATP and WTA Masters 1000 for the third time, but he has never made it to the championship match.
The four-time Grand Slam champion was untroubled by 27th-ranked Tien, capitalising on a double fault from the 20-year-old American for a break in the second game and cruising from there.
Sinner broke Tien four times and saved all four break points he faced, including two in the final game as he closed out the match in 66 minutes.
Zverev reached the Indian Wells semi-finals for the first time with a similarly comfortable 6-2, 6-3 victory over France’s Arthur Fils.
Zverev became just the fifth player to reach the semi-finals of all nine ATP Masters 1000 tournaments, an accomplishment he called “very special” as he joined a club featuring Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray.
He was in control throughout against Fils, who was coming off an impressive win over ninth-ranked Felix Auger-Aliassime.
Zverev broke the 21-year-old Frenchman to open the match, and his break for a 4-1 lead on a Fils double fault prompted a racquet-mangling outburst from Fils.
Zverev broke again at 4-2 in the second as he cruised to the victory, saving all three break points he faced.
“I think I played quicker today than the last couple of matches (against Fils). I think I took the time away and the ability for him to be extremely aggressive.”
Later quarter-final action features world number one Carlos Alcaraz — aiming to extend his unbeaten start to 2026 — as well as defending champion Jack Draper.
Spain’s Alcaraz, who lifted the Indian Wells trophy in 2023 and 2024, is on a 15-0 winning streak after following his Australian Open triumph with a title in Qatar.
He takes on 2021 Indian Wells champion Cameron Norrie, who beat Alcaraz in the second round of the Paris Masters 1000 last year.
Draper, back after missing the better part of six months with an arm injury, will face two-time Indian Wells finalist Daniil Medvedev.
