Zaki, who joins from Zamalek, made a big impact at Wigan Athletic last season before falling out with then manager Steve Bruce.
"The club has paid a significant loan fee to bring Amr back to the UK but his goal-scoring record with Wigan last season would suggest he will be a considerable asset in our fight to move up the Premier League table," a club statement said.
Zaki, known in Egypt as the Bulldozer, was unavailable for the African Nations Cup because of injury but is expected to join up with his new team mates this Friday and could be in contention for Hull's crucial relegation clash with Wolverhampton Wanderers this weekend.
Hull, who sit 18th in the Premier League, have to complete work permit and other red tape issues. "The playing contracts are signed," the club said.
"However, the final details must be undertaken before the loan can commence."
