كتب : Hatem Maher
Ashour Al-Adham put the visitors in front nine minutes before the break, thanks to a dreadful error from Zamalek keeper Mohamed Abdul-Monsef.
Defender Mahmoud Fathallah leveled the score from the spot early in the second period but Ahmed Galal sealed a precious win for Masri with 12 minutes remaining.
Zamalek lie fourth in the league table with 37 points, three adrift of Ismaili and Al-Gaish, who share second place- the final Champions League qualifying spot.
Masri, who enjoy a fine run of results since veteran striker Hossam Hassan took over at the club, are ninth on 25 points.
The Port Said-based club have gone through five matches unbeaten after the appointment of Hassan, who is yet to retire from professional football.
Zamalek coach Ruud Krol fielded skipper Hazem Emam to support attacking duo Abdul-Halim Ali and Mostafa Gaafar due to the absence of key playmaker Shikabala.
But once again Emam failed to put in a convincing display after giving away too many passes in midfield.
Zamalek produced a dull display in the first half and couldn't break through Masri defense.
An Abdul-Monsef blunder allowed Masri to go ahead in the 36th minute.
Al-Adham's weak free-kick astonishingly squirmed beneath the hands of Abdul-Monsef and into the net as Masri grabbed an unlikely lead.
Zamalek wasted a chance to equalize just before the break when Masri keeper George Owu failed to handle Emam's free-kick but none of the players pounced on the opportunity.
Dubious Penalty
Zamalek were awarded a dubious penalty six minutes after restart.
Gaafar was tugged by Mohamed Hafez inside the area but, although the contact was slight, the referee did not hesitate and immediately pointed to the spot.
There was a bizarre incident afterwards when the referee initially red-carded Hafez for what he thought as a second bookable offense.
However, he backtracked on his decision few moments later after finding out that it was the first booking for the defender.
Hassan rushed onto the pitch to protest the referee's decisions but his attempts were of no avail.
Fathallah stepped-up to convert the penalty and claim the equalizer for Zamalek, who hardly deserved to go level with Masri.
Substitute Sherif Ashraf, who was introduced in the second half instead of Emam, was unlucky to see his fierce drive cannon off the bar in the 58th minute.
Forward Galal broke Zamalek hearts in the 78th minute after being helped with a repeated error from Ahmed Ghanem.
A Masri free-kick deflected off the wall and went into the path of Gamal, who escaped the attention of Zamalek right-back Ghanem to poke home past Abdul-Monsef.
Watch the match's goals