Zhang won the first game 21-14 and was trailing 7-9 in the second when she went over on her left ankle.
The BWF Tournament Doctor treated her on court. She was visibly distraught and was wheelchaired off the field of play.
Zhang subsequently returned to the Olympic Village and saw Team USA medical staff. An ultrasound was performed and she was diagnosed with a ruptured Achilles.
She will fly back to Los Angeles on Thursday for surgery and is already mapping out her recovery and return to the court.
China’s He progresses to the quarterfinals of the Tokyo 2020 Olympic Games.