What is the ruling on paying Zakat for cars designated for rental, and is Zakat calculated on the annual revenue or on the value of the car itself, and what is the ruling on insuring these cars to exempt the renter from liability in the event of accidents?

Zakat is not obligatory on the leased cars themselves. Rather, it is obligatory on the rental income if each partner's share reaches the nisab (minimum threshold) independently or when combined with other wealth, and a hawl (one lunar year) has passed on it. The amount of zakat is 2.5%. As for commercial car insurance, it is haram (forbidden), whereas cooperative insurance is permissible.