OP, in addition to the advice above, you may also want to consider a search for all Milan airports, if MXP and AMS are both stops for you. Looks like AZ and KL both fly LIN-AMS rather than MXP-AMS. (There is no *A direct Milan-AMS, you would need to connect somewhere like ZRH, VIE, FRA, etc).

Also, when I searched on a few random dates, buying a Milan-AMS-Milan round trip was cheaper than buying a one-way fare. If you don't purchase this leg through AC, you may want to consider buying a round trip and just walking way from the second leg.

If you want to do the intra-Europe separately, then just use Matrix for YUL-MXP; AMS-YUL open jaw using GJS - yow's advice. If you use PowerTools, you can even book it directly on ac.com rather than having to phone in.