They now sit second in the league table with 50 points, just two behind leaders Ahly, who earlier in the day edged Ceramica Cleopatra 1-0.
Zamalek goalkeeper Mohamed Awad misjudged an easy cross from Pyramids winger Abdel-Rahman Magdi, allowing Ibrahim Adel—who was quick to follow up—to score easily from close range in the 21st minute.
Pyramids FC entered the match in a must-win situation to keep their championship hopes alive.
Zamalek, meanwhile, were in a similar position, although their chances of winning the league or securing a CAF Champions League spot had already been mathematically ruled out.
With two matches remaining, Zamalek remain third in the table with 41 points.
The White Knights have now gone four games without a win, with their last victory coming against Harras El-Hodoud last month.
Newly appointed coach Ayman El-Ramady has yet to record a win in his two games in charge.
On the other hand, Pyramids FC returned to winning form after back-to-back losses.
They now await the Egyptian Football Association (EFA) Appeals Committee's decision on Thursday regarding the Cairo derby— a ruling that could significantly impact the outcome of the league title.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)
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