Germany's Zverev and Auger-Aliassime both defeated Shelton and lost to Sinner to set up a winner-takes-all clash for the runners-up spot in the Bjorn Borg Group and Auger-Aliassime clinched a place in Saturday's semi-final against world number one Carlos Alcaraz.
"You want to be in the final but I'll have to go through a great player to do that," Auger-Aliassime said.
"I will take my chance if I have it."
Zverev was left to rue his failure to take any of his seven break points against Sinner, and it was a similarly frustrating story against the Canadian.
The German held break points in both sets but again could not make them count, and the Canadian broke Zverev at 5-4 up to take the first set, before going on to win the second set tiebreak.
Auger-Aliassime was put under pressure in the opening set, saving break points at 2-2 and 4-4, while Zverev came back from 0-40 down only to lose serve and hand the Canadian the set.
Zverev spent much of the second set gesturing to his team, with Auger-Aliassime winning his first two service games to love before both players were guilty of throwing away chances to break.
Auger-Aliassime let slip a 2-0 lead in the tiebreak, but when Zverev stepped up to serve at 4-5, the Canadian came through to earn consecutive minibreaks and send the German home.