Ferreira has been under fire since the club’s loss to archrival Ahly 3-0 in the Cairo derby on Saturday as the defending champions lost more ground in the title race.
After the game, Mansour said that the club board would hold a meeting to discuss the coach's future, before announcing that the meeting was postponed to Sunday.
“The club board voted unanimously on the sacking of Jesualdo Ferreira,” Mansour told a news conference on Sunday.
“We will announce the final decision regarding the Portuguese coach after Pharco FC game.
“The team’s results in the upcoming three games will have no effect in the club’s decision concerning the coach's future.”
Zamalek will face Ghazl El-Mahalla on Tuesday before meeting Future FC and Pharco FC on 29 January and 6 February respectively.
The defending champions failed to earn any win in the Egyptian league since the new year started, losing two games and holding in another two to fall to fifth place on the league table with 26 points, eight points behind leaders Ahly.
They also lost on penalties to Pyramids FC in the Egypt Cup semi-finals, exiting the competition.
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