One hour may be pushing it. In MXP, you have to be rescreened, even with connecting flights. When I went, there wasn't a line...it was a mass of people all surging forward aimlessly. A stampede would have had more organization.

On the other hand, I landed at 8 am. About an hour later (when I finally got through the checkpoints), the place had cleared out pretty decently...so maybe your 9 am arrival will be the latest one, and you'll get through pretty quickly.