A military or police armored personal carrier.
These vehicles are specifically designed to withstand infantry attacks. When they can hold off an angry mob of protesters, they can hold off a horde of hungry zombies. It takes an anti-tank mine, shaped charge or RPG to crack them, and zombies usually don't know how to handle these properly.
They are also equipped with machine guns which can be operated from the inside. And when they run out of ammo, you can simply run the zombies over. APCs weight tens of tons and reach speeds of over 100 km/h. That should be enough to crush even the sturdiest zombie.
If you can choose, you might rather want to get one with wheels than one with tracks. They are usually more fuel-efficient, reach higher speed on-road and still have good off-road capabilities, they aren't as noisy and they are easier to operate when you know how to drive a normal car.