Juan Cole thinks the Z-to-Z letter is a forgery, too

Here. For a Sunni-to-Sunni letter, it strangely uses Shiite phrasing, and ignores the meager and adversarial history between Zawahiri and Zarqawi. Cole concludes:

My gut tells me that the letter is a forgery. Most likely it is a black psy-ops operation of the US. But it could also come from Iran, since the mistakes are those a Shiite might make when pretending to be a Sunni. Or it could come from an Iraqi Shiite group attempting to manipulate the United States. Hmmm.

See my post from yesterday. Also, Eli at Left I on the News has been following this story suspiciously from the beginning.