You absolutely do not do that deal if you are the Tigers right now. In my opinion we have no need for a starter. Zumaya is an integral part of this years team.
If you trade for Smoltz (or anyone else for that matter), you give up a prospect that hasn't made it yet. That's the point of trading for an aging player, give up somebody that MIGHT pan out.
I can understand why you would want the trade being a Braves fan though.
We have a lot of young arms in AA and AAA, and even Ledezma right now in the majors. They would be a lot better to trade than Zumaya would be.