That's a tough choice, Hamilton is obviously a beast when healthy, but who knows how long that will last. Your pitching staff is solid, but Shields is due for a bit of a decline, which would concern me.
Zimmerman is the wild card, he just started rehab and if he comes back in the next two weeks, you can throw him in the UTIL spot and won't need Hamilton as much. Either you way you are depending on an injured player, but I personally would lean towards staying put unless Zimm has another setback.