كتب : Sherif Tarek
Mohamed Mohsen Abou-Greisha fired the home side ahead only after four minutes, and Mostafa Karim added the second on 17 minutes.
Abdul-Halim Ali pulled one back for the White Knights ten minutes later, and Karim notched the third in the first half injury time.
Ismaili are now at the top of the league table with 57 points, three ahead of second-placed Ahli.
The Red Devils have three games to go, while the coastal side only have two.
Both teams will face each other in a decisive play off if they remain tied on equal points till the end of the season.
Zamalek remain in sixth place with 38 points, and the defeat, their tenth this term, marked their all-time worst record of losses in one season.
Starting Line-up
Ismaili had Mozambican center-half Dario Khan and striker Mohamed Fadl on the sidelines due to suspension and injury respectively.
Mohamed Mohsen Abou-Greisha partnered Mostafa Karim upfront, while Ibrahim Yehia deputized for Khan.
On the other hand, Zamalek fielded pretty much the same starting line-up which impressed against Ahli last week. The only difference was playing Alaa Ali instead of Ahmed Abdul-Raouf in midfield.
Goalkeeper Abdul-Wahed Al-Sayed retained his place between the sticks to rubbish recent rumors that Mohamed Abdul-Monsef will have a go.
Control
Early in the first half, Ismaili took control of the match, which was held behind closed doors as the stands of the stadium are still closed for renovation.
Abou-Greisha hit the opener after he chested home an Abdullah Saied left cross from point-blank range.
Zamalek, who raised eyebrows in the Cairo Derby on Thursday, were clearly out-of-sorts and some sloppy defending could have cost them more than three goals.
Amr Adel was close to scoring a leveler for the Cairo side from inside the penalty area, but his tame effort was easily blocked by Ismaili goalie Mohamed Fathi.
Iraqi ace Karim doubled Ismaili's lead when he volleyed Ahmed Magdi's awkwardly-headed clearance right in front of the box.
Ali netted a controversial goal three minutes from the half hour mark, after he collided with Fathi in the box while slotting home from close proximity.
A minute earlier, the veteran striker set up Sherif Ashraf with a precise cross, but the latter mis-hit his shot.
Zamalek had several more chances afterwards, but to no avail.
Minutes from the interval, an unmarked Karim received a corner-kick in good position to slide past Al-Sayed.
Uneventful
After the restart, the visitors seemed willing to make amends for their first-half lackluster performance, and tried to pile up pressure upfront.
But all in all, the goalless second period was clearly an uneventful affair.
Michel Decastel sent playmaker Shikabala in instead of striker Ashraf, in an attempt to shore up the frontline.
Ismaili, who became dangerous on the counter attack, could have earned a three-goal cushion when Abdullah Saied released a powerful shot, but it stung Al-Sayed's palms.
Zamalek managed to have the upper hand, in terms of ball possession, but struggled to carve out close chances. Ricardo's men also lost their edge in the second half.
Six minutes from time, Hazem Emam tried his luck with a curling shot, but Fathi parried it away to inhibit the Zamalek youngster from reducing the arrears.
Shikabala also failed to convert a free-kick three minutes later when his drive went high over.