The News understands the Blues have agreed a one-year loan deal for the controversial Egypt international.
Zaki looks set to have his arrival rubber stamped by the end of this week to boost Paul Hart's striking options following the departure of Peter Crouch to Spurs for £9m.
The El Zamalek striker met his club's board on Monday to discuss the Pompey offer.
That was given the green light, paving the way for man who hit 11 goals while with Wigan last season to move to Fratton Park.
Pompey's stuttering search for much-needed reinforcements finally accelerated yesterday on a hectic afternoon of activity which saw:
Right-back Steve Finnan pen a one-year deal on a free transfer.
Blues boss Paul Hart make a move for Cardiff striker Ross McCormack.
Croatia international forward Nikola Kalinic arrive in England in the hope of sealing a deal with Pompey.
Reports today also suggest Stephen Hunt is poised to join in a £3.5m deal from Reading, while keeper Antti Niemi could arrive as back-up to David James.
Spanish side Malaga have also shown a strong interest in 26-year-old Zaki, but it looks as if Pompey have won the chase for his signature.
The powerhouse proved a big hit while on loan at Wigan last season but fell out of favour with then-Latics boss Steve Bruce after twice returning back to training late after international duty.
Zaki could be joined at Pompey by Kalinic, who last night landed in London ahead of a medical.
The 21-year-old flew into England via Vienna as his potential move to the Premier League moved on.
There is still a distance to go before a £5.5m deal is completed, though.
Pompey have yet to agree a fee with Hajduk Split for the striker, and the terms of payment could yet kill the move.
Hajduk are understood to want the bulk of the fee up front, while the Blues want the money spread over a long period.
Kalinic missed his scheduled flight into England as they awaited confirmation of Pompey's offer. They later received paperwork but were not happy with the terms of the deal, according to sources.
McCormack could emerge as a serious alternative, with chief executive Peter Storrie yesterday contacting Cardiff over the Scotland international.
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