No. 4 seed Muguruza is likely to face Qiang Wang in Saturday's semifinal.
Wang - who has been touted by some as a potential successor to Chinese tennis icon Li Na - was chasing her third title but was never in the match, which was over in little more than an hour.
Zhang, who has won two career WTA singles titles and was knocked out of Beijng by Japan's Naomi Osaka at the quarter finals, will be favourite to win against 18-year-old Yastremska, now ranked 102.
Wang had grabbed headlines at the French Open with her straight-sets demolition of Venus Williams, offering a hint of what was to come, and later overcame Karolina Pliskova in both Beijing and Wuhan.
Fiscalía turca pide 12,5 años de cárcel para Arda Turan
En las imágenes de 'Magazinn TV', que fueron captadas por distintas cámaras, puede verse cómo Arda Turan se encara supuestamente con el cantante.
Until Sunday, Yastremska s chief claim to fame had been 2016 Wimbledon girls singles finalist, but earlier this year she became the first player born this millennium to break into the WTA top 100 rankings.
Dayana Yastremska into her first WTA final at the @HKTennisOpen! "Yesterday she was playing really great tennis - I was missing a lot, my game was really off". "I just went for it", Wang said at the close of her marathon day.
The Rome champion, who had been hoping to sew up qualification in Hong Kong for the WTA Finals, said Saturday that she was a "fighter" and had come back on court believing she still had a chance. "Every tournament I play, every match I play my goal is to win, to ideal myself, to get experience and to win one day a Grand Slam", she said. As reported by our website, if our compatriot will miss the competition this week, she may not qualify for the Final tournament in Singapore in connection with the insufficient number of rating points.
China's top-ranked player is making a run at the top 20.
Second-seeded Frenchwoman Caroline Garcia booked her spot in the semifinals after sixth-seeded Croatian Petra Martic retired during the second set of their match, with Garcia leading 6-2, 1-0.
"I was nervous from the first ball", Yastremska said.