I think 15m is a little low for Zito. I'm guessing 16-18 for a young guy who has a Cy-Young. Wang, Zito, Mussina, Lilly and Johnson isn't a bad rotation, except that--of late--Lilly and RJ get pounded and Mussina is a huge injury risk. Zito throws more walks than anyone in baseball and Wang, while good, is young and a groundball pitcher at best. It's definitely not doom-and-gloom for the Yankees pitching (especially with Hughes in the wings), but I would take the Sox rotation (w/ Matsuzaka, god willing) over that one any day of the week.
getting anything for two overpaid losers is a good deal. Trading Wright is remarkably similar to something the sox haven't (and won't) been able to do: move Matt Clement. So Kudos for being able to do that. Of course, Pavano and previously Kevin Brown are two other guys who you would have liked to move but weren't able to, so its not a "full kudos" to Cashman over the years. As for Sheffield, I think it was pretty even as far as a deal goes. it is easy to forget how good Sheffield is as a hitter, with his injury and the power of the Yankees lineup around him. In this market he would have been a 16m at least FA for Detroit, so they're happy to get him. That's no coup.
I would rather have Matsuzaka and so would the Yankees and so would you.