The Angolan striker needed five minutes to fire Ahli in front after once again making the most of his aerial prowess.
He rose above his marker Moatassem Salem to head Gilberto's free-kick from the left past Ismaili keeper Mohamed Sobhi.
Versatile midfielder Ahmed Fathi, who scored the invaluable winner against Gaish on Wednesday, unsettled Ismaili's defense through his energetic moves.
He could have doubled Ahli's advantage in the eighth minute when he latched onto a through pass from Mohamed Abou-Treika to go clear on goal but a last-ditch interception from Dario Khan deflected his shot over the bar.
Ismaili began to find their rhythm afterwards, thanks to the tireless work of natural central defender Sherif Abdul-Fadil, who played as a right winger.
Abdul-Fadil got the better of Ahli's left wingback Gilberto more than once to help Ismaili pile on pressure.
The Dervishes' midfielder Mohamed Hommos was unlucky to see his powerful right-footed shot strike the bar on 25 minutes.
Playmaker Abdullah Saied also threatened Ahli keeper Ramzi Saleh when he shot on the turn from inside the area but the Palestinian parried his effort.
Despite Ismaili's pressure, Ahli still had the better chances to increase the gap after some neatly-worked counter attacks.
On 30 minutes, the evergreen Fathi skipped past two defenders and went one-on-one with Mohamed Sobhi, who superbly blocked the Egyptian international's low shot.