Medvedev has been a model of consistency on hardcourts this year with titles in Rotterdam, Doha, Dubai and Miami and though the Russian world number three was not at his dominant best he battled past Humbert for his 41st win of 2023 on the surface.
"I'm happy that I managed to raise my level in important moments, except a game in the second set," Medvedev said.
"It's great that I managed to still find in this tough match these moments of consistency, which is enough to win.
"That's what you have to do. I'm happy to be in the semi-finals. When you come to the tournament, you always want to go as far as possible. Happy to still be here tomorrow.
"The further we go, the tougher the matches, the tougher the opponents. That's normal."
Chengdu champion Zverev, who is rediscovering his best form after a serious ankle injury last year, extended his winning run to seven matches with a 6-1, 6-7(5), 6-3 win over Chile's Nicolas Jarry.
The 10th-ranked German has lost three times to Medvedev this year but flipped the script in their last meeting in Cincinnati.
"It seems like we have to play each other every tournament this year. It's the fifth time we're going to play each other," Zverev said. "Every time we play, it's a battle.
"I'm looking forward to what's to come. He's playing great tennis. I hope I can bring my A game."
Later on Monday, top seed Carlos Alcaraz and Italian Jannik Sinner set up yet another instalment in their blossoming rivalry with quarter-final wins over Casper Ruud and Grigor Dimitrov respectively.
Alcaraz beat Ruud 6-4, 6-2 in straight sets to seal a spot in the semi-final, while Sinner had to dig deep and overcome illness to clinch a 6-4, 3-6, 6-2 win over Bulgaria's Dimitrov.
"A very tough evening, the level was really high," Sinner said in his on-court interview.
"I didn't feel very good, maybe I ate something wrong. At one point I also threw up a little, but I'm happy with how I handled the situation."
SWIATEK AND GAUFF SOAR
In the women's tournament, world number two Iga Swiatek powered into the second round on her Beijing debut with a 6-4, 6-3 victory over Spain's Sara Sorribes Tormo.
The Pole was particularly effective at the net, winning 15 out of 17 points, and next meets Frenchwoman Varvara Gracheva.
"Today I felt really confident and comfortable because I've been practising that a lot," Swiatek said.
"I'm pretty proud of my performance at the net because, technically, I feel like my volley has changed. I'm really happy with that.
"I think against some players it's necessary to go to the net and today that was that kind of a match."
US Open winner Coco Gauff roared to victory in her first match as a Grand Slam champion, as the American downed Ekaterina Alexandrova 7-5, 6-3.
Fresh from her triumph in Ningbo last week, world number seven Ons Jabeur eased past 19-year-old Osaka champion Ashlyn Krueger 6-3, 6-4.
"It was a great match," said Jabeur. "I played the next generation. She's a really good player. She's going to be one of the top players in the future."
The Tunisian, who is looking to qualify for the season-ending WTA Finals, plays Marta Kostyuk in the second round.
