I would like to see Zappe play 2 more games, against Chicago and the Jets.
First, Mac is nowhere near 100%.
Second, if Zappe ends up sucking in either of those games, you end the QB controversy, Jones goes back in and very few, if any, question his return.
Third, if you put Jones back in now against Chicago, or next week against the Jets as his first game, and he gets destroyed, you're in the worst possible QB controversy situation, and with Jones at less than 100%, that is even more likely to happen....which isn't fair to him, either.
Fourth, if Zappe excels against Chicago, and then follows that up with a convincing performance against a "good team", the Jets, then you have a pretty good body of work to measure him by, and have a much better idea of his ceiling.
Two more starts for Zappe...and if he blows it in either game, you end the QB controversy and Jones returns stronger and with less of a monkey on his back. Seems like a no brainer to me. Gives Mac maximum time to get healthy, gives the team a solid body of work against a variety of opponents for Zappe.
Best case scneario, Zappe wins both games, and you end up with a QB controversy with two good QB's. Worst case scenario, you lose one or both games with Zappe, Mac gets two more weeks to heal, and comes back to end the controversy.