Zero-Emission Vehicles Act of 2018 This bill amends the Clean Air Act to establish a zero-emission passenger vehicle standard. Specifically, the bill sets a schedule for increasing the percentage of zero-emission vehicles a vehicle manufacturer must sell, culminating in a requirement to sell only zero-emission vehicles by 2040. The bill also sets forth a zero-emission vehicle credit program that approves one zero-emission vehicle credit for each zero-emission vehicle sold in the United States.