Your 'curved' version looks much better to the eye than your stretched out 'lambo' version. Always take into consideration the way the car is *really* shaped, because the argument of "it's stylized!!11!!one" is one I've seen and heard over and over and over again. A paper cup with a hole in the bottom holds more water than that old line.
Take into consideration that the windshield is glass, and it's going to reflect and refract and shine...you won't see straight through it to the seats, and if it's tinted, it won't be flat black. Even with simple vectors like you're using you can achieve more than what you're giving us.
Pick one direction, and one direction only for a light source if you're new to shading, and just use one color (blue, green, orange, purple, your options are limitless on a black car), and remember that your shadows will not be symmetrical on both sides.
Highlights will follow the ridges of the separate pieces just as much as shadows follow the dips. And on metal, there's usually a bright white against a dark black somewhere, even if it's just in one place. So if you're going to shade, don't do it halfway, it just looks bad.
Here's an image to illustrate what I mean. The light gray shows your highlights, and the red your shadows.