That's because you're too far from the origin. You have to zoom out, move the camera view with your RMB and then you can zoom in. It's very annoying, I onow.

When I move the camera and zoom in, same thing, Cant zoom

@Stephan3321 This is the same for most 3D software. This is due to the maths when you get very close to the control target. Just press 0 on your keyboard and it will reset the camera (or go in the camera menu and choose reset).

Ok, Thanks