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.
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.