Al Ahly were out for revenge having lost to the Mexican club in last year's third-place play-off but their mission did not start well.
Only three minutes were on the clock when Neri Cardozo slotted past Sherif Ekramy after sweeping up Humberto Suazo's fine through ball.
The Egyptians were level five minutes later, Emad Meteab controlling a cross from deep on the left wing and squeezing home at the near post.
Trezeguet soon went close to completing the quick turnaround, only for his shot to come against a determined Juan de Dios in the Monterrey goal.
However when Delgado put the CONCACAF champions back ahead in the 22nd minute, all of a sudden Al Ahly's defence began to crumble.
Five minutes later Leobardo Lopez beat Ekramy with a powerful drive from a corner and the Mohamed Youssef's Egyptians were on the ropes.
They did not help themselves one minute before the break either, as captain Wael Gomaa fouled Lopez to concede a penalty that Suazo coolly converted.
It was a less frenetic second half but it was marked by a record-breaking moment as Delgado tucked away Suazo's dinked pass beyond Ekramy to bring up his fifth goal in the competition.
He surpassed the four-goal tallies of previous leaders Lionel Messi, Denilson and Mohamed Aboutrika.
Weary Al Ahly were most definitely out of ideas by the late stages and were only spared the ignominy of shipping a sixth goal by Suazo's faulty radar as time ticked away in Marrakesh.