The Whites took a stranglehold on the game in the early minutes to take an early lead but suffered an inexplicable dip in form later on.
ENPPI capitalized on their opponents' shaky form to reply with three goals and end the game in a deserved 3-1 win.
Zamalek coach Hossam Hassan took a swipe at his men after the match, saying they were spiritless and completely out of sorts.
Gaber conceded that he was not up to scratch and vowed to produce much better displays in the Cairo side's upcoming games.
"I must admit that I was one of those players who were completely off-form. We deserved to be blamed," he told Zamalek's official website.
"Our form suddenly plummeted and I really don't know why.
"I will be working my socks off to make it up for the fans."