You're in aperture priority AE when you use exposure compensation, so you choose your compensation setting & leave the dial alone. The camera sets the shutter speed for you, you choose the aperture.
So the answer is no, you can't use the shutter speed dial for anything else when it is set in exposure compensation, but then there is no need to. If you move it off exposure compensation, you are either moving to "A" (regular AE without compansation) or to manual & are selecting your own shutter speed.
Yes, the dial is set for 1/3 stop increments of exposure compensation, but shutter speeds are continuous (stepless) in AE so the speed might actually be slightly off what you set for even more accurate exposure. If you want a specific shutter speed, then you choose manually. FWIW the ZM lenses also have aperture settings in 1/3 stop increments