كتب : Ahmad Saied
Defender Mohamed Sedik headed home to give Zamalek the lead but Sherif Farouk snatched the equalizer midway through the second period.
The draw kept Zamalek second with 46 points, four behind leaders Ahli, who still have two matches in hand.
Koroum moved up to the 12th place, third from bottom, on 17 points and still battling to keep their place in the first division next season.
Koroum ended Zamalek's three-game winning run and forced the Cairo club to concede their first goal at home since February.
Zamalek grabbed the lead in the 20th minute when Sedik towered to Yousef Hamdi's cross to head the opener home.
Koroum almost snatched the equalizer after two minutes but Ashraf Al-Sayed's powerful header was denied by the post.
International striker Abdul-Halim Ali squandered easy chances after the break and Koroum replied toughly.
In the 73rd minute, substitute Mohamed Abdul-Salam raced down the right and crossed for the darting Farouk who ghosted behind Zamalek's static defenders and buried the ball home.
Ghanaian midfielder Awuley Quay 'Junior' failed to restore the lead in the dying seconds when he fired wide from five meters with the goal at his mercy.