Edwin Jackson is having the best year of his career (strikeout rate well above average, and far less hittable than he has ever been before), one year after he pitched a game in the World Series - a game, and a Series, that his team won. It was actually Jackson's second World Series appearance; in 2008, he pitched two innings in relief, surrendering a solo home run but only one other baserunner.
As for Jordan Zimmermann, I believe he is growing tired after a longer season than he's ever pitched before. But I also believe he is a very good pitcher, and that you spelled his name wrong.
Gio - JZ - Detwiler - Jackson is a very good top 4 that alternates lefty and righty without letting up on the power. I actually believe the key is preserving Detwiler's new tough-guy mentality. If Det shows the competitiveness and endurance he's demonstrated this summer, we will go deep into the playoffs.