The Allievi will play either Sao Paulo or Real Madrid on Friday
The goals all came in the second half and were scored by Zucchetti and two from Agnero.
Milan will now play the winners of Sao Paulo-Real Madrid on Friday with the kick-off at 13.35 CET.
The Rossoneri had to battle for victory but they came through despite injury to Altare but Agnero took his goal tally to five so far.