All the goals came in a pulsating first half at the San Siro. Ibrahimovic also scored a penalty, while Thiago Silva and Alexandre Pato were on the scoresheet.
Milan is a point behind Juventus, which has a game in hand.
Earlier, Inter Milan needed a last-minute goal from Luc Castaignos to beat 10-man Siena 1-0 and edge further away from the relegation zone with its second league win in a row.
Inter leapfrogs Fiorentina, which lost 2-0 at Palermo.
Also Sunday, Adrian Mutu’s double gave Cesena a 2-0 win over Genoa, and Cagliari drew 1-1 with Bologna.
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