Some credit cards include hire car insurance, which covers you when you hire a car. Sometimes Zipcars falls under this coverage. 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 payment 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 from Zipcar. Please email firstname.lastname@example.org to request this documentation.