كتب : Hatem Maher
Abdullah Othman fired the visitors in front early in the first half but Zamalek's Brazilian full-back Ricardo Alves equalized in the 25th minute.
Karim Adel restored Olympic's lead shortly after as Olympic went to the locker room with an unlikely lead.
The Alexandria-based club had Mostafa Fouad dismissed early in the second period, but despite their numerical disadvantage, they extended the gap via Mostafa Moushir's goal.
A below-par Zamalek side failed to get anything from the game to lose ground to arch-rivals Ahli, who defeated Ittihad 2-1 earlier in the day.
The White Knights slipped to fourth spot on 16 points, two adrift of leaders Petrojet, who played an extra match.
A traditional two-horse race for the league title is expected. If Ahli and Zamalek won their rescheduled matches, they would occupy the top two spots, with the former holding a three-point lead.
Newcomers Olympic moved into 11th place with 10 points from nine games.
Left-back Ricardo was unlucky to saw his fierce free-kick cannon off the bar in the first minute.
But it was Olympic who astonishingly took the initiative to stun the home crowd.
Ghanaian midfielder Othman cut ahead of his marker, Mahmoud Fathallah, to receive a right-wing free-kick with a delicate header that left Abdul-Wahed Al-Sayed with no chance.
Ricardo, who put in his finest display since joining Zamalek in the close season, drew Zamalek level in the 25th minute.
His angled free-kick deflected off a defender's header to wrong-foot Olympic's Ghanaian keeper Caesar Ekow.
Striker Karim Adel restored Olympic's advantage five minutes later after capitalizing on a miserable defending from debutant Amr Adel.
Adel, who moved to Zamalek from Gaish, mis-hit his clearance to allow Karim Adel gather the ball and go clear on goal.
His initial shot was palmed by hapless keeper Al-Sayed, who could do nothing to prevent Adel from scoring the rebound.
Angry Chants
Olympic had defender Fouad sent off nine minutes after the restart.
The 28-year-old received his marching orders for a second bookable offense after a needless tackle on Ricardo.
However, Zamalek not only failed to capitalize on their numerical advantage, but they also fell behind further.
Moushir added a third in the 67th minute to widen Zamalek's misery.
Fathallah bravely blocked a powerful low shot but the ball slipped into the path of the unmarked Moushir, who fired home from close range.
That goal was the straw that broke the camel's back. Zamalek fans hurled insults at their own players, technical staff and board.
They even cheered for the visitors whenever they had the ball.
It remains to be seen whether German coach Reiner Hollmann would stay at the five-time African champions after Zamalek's repeated dismal showings.