When is this trip? That will,affect your plans regarding Lake Como.
If this is a spring or summer trip, and you are traveling between Nice and Zurich, I suggest you head to Varenna for your Lake Como time ( two nights recommended). Then continue North on the train to Tirano, where you can use the Bernina Pass route as your avenue into Switzerland. It does not necessarily have to be the designated Bernina Express train; regional trains ply the same tracks hourly and view the same scenery.
This route is much more scenic than the Gotthard route taken by the direct train from Milan to Zurich. That train does stop in the town of Como, but it is not as nice as Varenna. And then the train uses the long and deep Gotthard Basistunnel to go under the Alps--you will be in the dark tunnel with no views of the peaks at all.
As for Milan, I will say that the kindest and most welcoming people we met in all of Italy were in Milan. Maybe because they were not tired of tourists? We spent our last night of a trip with our daughters there, with tickets for the ballet at La Scala. We stopped by a pharmacy to get some ear medicine for my husband, and left there with not only the appropriate medication, but a bag full of high-end skin-care samples offered to the teen girls and to me by the cosmetologist. She knew we were tourists and would not be returning to buy, but was very generous and discussed the use of each product, then packaged it all in a lovely bag that I still use today.
Then we went to Princi to get focaccia sandwiches (the best in the world) for a picnic dinner on our deck at the hotel prior to the ballet. I spied a deli across the street and went in seeking some salad and maybe wine. The broccoli salad was perfect, and when Inasked if they sold white wine he said "Of course. Would you like it chilled?" (he spoke in Italian, but slowly and clearly). Then he proceeded to determine what else we might need----forks for the salad? Plastic cups for the wine? Did we have a corkscrew for the wine, or should he open it and replace the cork? I hadn't thought this through and of course did need all of that, which he provided for free and with a smile. I left with everything in a nice plastic bag, for €8 total.