Some credit cards include rental car insurance. Zipcars could fall under this coverage depending on your credit card provider. Give them a call to see if they'll cover you in a Zipcar.
If you are covered by your credit card, make sure to use it to pay for your reservations. You can update your credit card info here.
If you've been in an accident while driving a Zipcar and you've filed a claim with your credit card company, they will want to see documentation. Please contact Sedgwick CMS at 1-866-345-2474 to request this documentation.