The main goal of the TC is not just to prevent collusion. I think that everyone here is honorable enough (outside of me) to not pull such a trick. The TC, along with RC, EC, and any other C is here to protect the integrity of the league.
Any time one of these trades get vetoed everyone goes on to attack the TC. They(we) do not have any easy job of it. I think anyone that helps out to make this league better should be commended for it. We don't get paid, and we do it for the benefit of everyone in this league, in order to make it enjoyable. In other leagues that I have played in, trades are vetoed based on perceived value being exchanged.
That being said, I have great respect for both GMs and I am sure you guys can come up with a more even keeled trade. Regardless of Z's bad contract he is going to pitch next year, and that in and of itself will have value. And Ells is an elite performer who put up 3,000 point seasons before the power spike.