It is just as difficult to accelerate a car on a level horizontal surface on the Moon as it is here on Earth because

Mass of the car is independent of gravity

Explanation:

Here, we want to state the reason why even though we have the acceleration due to gravity absent on the moon, it is still difficult to accelerate a car on a level horizontal level on the moon.

The answer to this is that the mass of the car that we want to accelerate is independent of gravity.

Had it been that gravity has an effect on the mass of the said car, then we might conclude that it will not be difficult to accelerate the car on a horizontal surface on the moon.

But due to the fact that gravity has no effect on the mass of the car to be accelerated, then the problem we have on earth with accelerating the car is the same problem we will have on the moon if we try to accelerate the car on a horizontal level surface.