كتب : Ahmad Saied
Substitute Magdi Attwa, who was introduced at half-time, scored the winner in the 56th minute after a silky pass from Amr Zaki.
But Attwa left the pitch in the 78th minute with a knee injury and was replaced by Moetazbellah Mohamed 'Eno'.
New-signing Attwa told Egyptian Satellite Network Dream TV after the game that he was knocked by Ismaili international midfielder Hosni Abd-Rabou apart from action.
Zamalek's ninth successive league victory over Ismaili moved them six spots up to settle in third place on 13 points while the losers remained in charge of the table with 16.
Ismaili had the first chance of the game in the ninth minute when a quick blitz from Abdullah Al-Saied and Ahmed Fathi ended at the feet of Omar Gamal who fired wide.
Abd-Rabou denied Zamalek a certain goal two minutes later as he towered to clear Amr Al-Safti's header just before crossing the goal line.
Zamalek keeper Mohamed Abdul-Monsef was called upon in the 22nd minute when he palmed away Moetasem Salem's powerful header from close range.
Attwa and Abdul-Halim Ali were fielded after the interval, replacing captain Hazem Emam and Ghanaian playmaker Awuley Quaye 'Junior', who lacked sharpness after a long layoff.
The visitors grabbed the lead shortly after when Zaki, who returned to the starting line-up after being declared fit to play as heart worries ruled him out of recent games, changed directions to sidestep Abd-Rabou and slip a neat pass to Attwa.
With his marker caught napping, Attwa went one-on-one with Ismaili keeper Amer Shafie and planted an ice-cool finish past the Jordanian international.
Ismaili attacked in numbers searching for the equalizer, leaving wide spaces into their last third that could have resulted in more goals.
Ali was set-up twice with the goal at his mercy but he failed to convert the ball in both times while Shafie blocked a couple of chances from Alaa Abdul-Ghani and Zaki.
Ismaili dominated the rhythm but never threatened the goal as Zamalek defenders and keeper tightened their grip on the precious three points.