There were several ways forward after Jones returned: 1. The team is losing and Jones stinks. 2. The team is losing but Jones plays well. 3. The team is winning and Jones is good. 4. The team is winning and Jones stinks.
In scenarios 2 & 3, Jones certainly continues to play. In scenario 1, I think Jones likely continues to play (unless he was putrid and turning the ball over in spades) because there's nothing to play for. Scenario 4 - which is the one we're currently experiencing - is the most fascinating because I think the pull to potentially play Zappe (if you feel he gives the team better quarterback play) is the strongest, since that scenario involves the team potentially finding themselves in a position for a playoff run.