Jeff Withey for some flotsam player and maybe a protected second-round pick almost makes too much sense to not happen.
Is Withey better than Zeller? Never heard of a "protected" second round pick?
Top 55 protected picks are actually quite common when a team trades for a player that another team no longer has a need for. Since the team trading the player must be reimbursed in some way, the accepting team sends a top 55 protected pick (that will likely never be transferred) to essentially circumvent the trade rules.
And, I agree - might as well just keep Zeller.