Peavy For Zambrano?

While its purely speculation at this point, there has been some buzz recently regarding a Second City swap of Jake Peavy and Carlos Zambrano.  Peavy, as you may remember, listed the Cubs as a team he was willing to be traded to when the Padres first looked to move him.  Zambrano has solid numbers for the year, posting an ERA of 3.69 and 8 strikeouts per 9 innings.  With just two starts in black and white, people are already wondering if Peavy will be a part of the team's 2010 plans.  Big Z has had a very strong September (2.81 ERA, 38 K's in 32 IP) but frustrations on the north side of Chicago have put every Cubbie under the gun.Starting in 2010, the continuation of Peavy's contract will pay him $52MM over three years plus a club option.  Zambrano will earn $53.75MM in the next three years with a vesting player option for 2013 worth $19.25MM.Could an intra-city trade of this magnitude ever happen?  Should either team pursue such a trade or is this simply a case of the gr...