The MZ DLC is NOT canon! If that is the case, then why not just say that Dr. Who, Godzilla etc. are all canon too. The only things that are canon at the moment are the Classic Fallout's, parts of Fallout Tactics, Van Buren, and perhaps bits and pieces of Fallout 3(mind you that is debatable).
Sorry, bud, but MZ IS canon unless Bethesda says otherwise; or if Bethesda sells the rights and the new company says it isn't canon.
If I recall, I had a thread/poll regarding the cannonicy of FO3; the majority said that it was Canon, a minority said that FO3 was too different to be canon, and only 5 votes out of the 190+ votes said that it's not canon unless made by the origonal devs. Of course, I may need to run a new poll regarding MZ to see if it's not universally despised...