The Brembo & non-Brembo master cylinders are the same size. You will see two different part numbers for MC's and while I haven't researched
why I'm betting the different is for VDC and non-VDC equipped Z's.
If you haven't already, you might want to consider adding steel braided brake lines. Brembos came stock on my Z and the pedal has never felt as firm as my 240 did after I upgraded all of its braking components. Still, the Z's brakes are tireless and I can out brake nearly everything on the road. A good bleeding should help firm up your pedal feel, but I don't know that it will ever be "rock hard". What pads and rotors are you running? I suppose since you're in Italy actual Brembo stuff is much cheaper than it is the states!
Enjoy Italia! One of my military regrets stems from me missing getting stationed in Vicenza with 173rd by about a week. Things work out though, I went to Germany and was stationed a few minutes away from Zuffenhausen.
