Runner-up last year to Jannik Sinner, Zverev lived up to his third seeding with a hard-earned 6-3 6-7 (5-7) 6-1 7-6 (7-3) victory over rising American Learner Tien in melting Melbourne on Tuesday.
The German will next meet world No.1 Carlos Alcaraz, who knocked out home hope and sixth seed Alex de Minaur 7-5 6-2 6-1 in the late match.
The Zverev-Tien contest was played entirely under a closed roof on Rod Laver Arena as the mercury soared past 40 degrees.
With seven of Zverev's 24 career titles coming indoors, including two at the season-ending showpiece, the German was always going to prove a tough customer for 20-year-old Tien, the youngest AO quarter-finalist since Nick Kyrgios, at 19 years and eight months, in 2015.
After taking out three-time finalist Daniil Medvedev in round four, the US challenger won the second set in a tiebreaker and Zverev needed 24 aces to subdue the exciting youngster.
The 29th seed and lowest-ranked player to make the last eight at least made a stand, threatening to force a deciding fifth seed before the world No.3 prevailed after three hours and 11 minutes.
"Learner from the baseline was playing unbelievable," Zverev said.
"I don't think I've played anyone who plays that well from the baseline for a very, very long time.
"I don't know what (coach) Michael Chang has done with him in the off-season, but the way he's playing, it's incredible.
"Without my 20 aces, or something like that, I don't think I would have won today.
"So obviously very happy with my serve but, generally, happy to be back in the semis."
Zverev is into his 10th grand slam semi-final in total, second only among active players behind the great Novak Djokovic.
But while Djokovic is chasing an unprecedented 25th grand slam singles crown this year at Melbourne Park, Zverev is stilling hunting a first.
The 29-year-old lost to Dominic Thiem in the 2020 US Open final, to Carlos Alcaraz in the 2024 French Open decider and to Sinner in straight sets last year in Melbourne.
At least he will enter Friday's semi-final feeling ready to compete at full fitness.
"The last 10 days I felt healthy, which is very nice, and pain-free, which I haven't felt in a long time - probably in 12 months," Zverev said.
"So that's a good starting point for me.
"I feel good. I feel like I'm playing well. I feel happy on the court because I am playing pain-free and I'm playing good level.
"Of course, winning always helps. When you are winning, you are always happier automatically as an athlete."
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