Ibrahimovic, Milan overwhelm Palermo
Ibrahimovic fired Milan in front in the 22nd minute and benefited from another Robinho assist just after half an hour before completing his treble with a stunning long-range shot in the 35th.
The Sweden striker would have added to his first-half tally but for a wonder save from Palermo goalkeeper Emiliano Viviano.
Thiago Silva completed the rout shortly before the hour mark.
Milan heads into the second leg of its Champions League last-16 matchup with Arsenal with even more confidence. Leading 4-0 from the first leg, it will expect to complete the job in London on Tuesday.
It is Palermo's second hefty defeat in a row, and its third loss in its past four games - although it is the first time the Sicilian side has lost at home this year.
Milan started lively and would have taken an early lead but for some woeful finishing. Antonio Nocerino, Urby Emanuelson and Sulley Muntari all had efforts off target.
The defending champion went in front when Muntari slipped but fortunately managed to intercept a Palermo pass and get the ball to Robinho, who touched in for Ibrahimovic to curl into the top left corner.
Palermo, which was routed 4-1 at Siena last week, searched for the equalizer and almost got it as the ball pinged around a crowded Milan penalty area before the Rossoneri managed to scramble it away.
Straight from that, Milan went on the counterattack and Robinho again found Ibrahimovic, who controlled well before cutting inside and firing into the left corner.
Ibrahimovic grabbed his third four minutes later when he whipped the ball into the bottom right corner from 25 yards.
The former Inter Milan star could have had another in the 39th but Viviano somehow managed to deflect Ibrahimovic's six-yard effort to safety.
Milan came close to extending its lead seven minutes after the break but Viviano did well to turn Thiago Silva's free kick around his right post. The Palermo goalkeeper pulled off another good save moments later to deny Stephan El Shaarawy.
However, Viviano could do nothing when El Shaarawy's cross was headed in by Thiago Silva
Palermo almost got one back minutes later when Edgar Barreto's effort crashed off the left post.
It was Ibrahimovic's first game back following a three-match ban for slapping Napoli defender Salvatore Aronica. It takes his tally to 18 for the season as he draws level with Udinese forward Antonio Di Natale at the top of the goalscoring charts.