Zimmerman wasn't a FA signing so he can't be free dropped.
You can use a new owner buyout on him though:
There are three options to buy out a contract:
Option 1: Team pays 25% of the remaining contract during the following season.
Option 2: Team pays 40% of the remaining contract, spread over the following 2 seasons.
Option 3: Team pays 50% of the remaining contract, spread over the following 3 seasons.