By lowering your overall field of view while decreasing the apparent distance of the objects at the center of your vision.
Which is what the definition of zoom is, really.
You are wrong. It has been explained many, many many many many many times on this forum especially during the beta. It is not zoom, it appears to be zoom because people are so conditioned from previous gameplay experience. But it is just a function to allow you to see the environment at the same level of detail an actual human would be able to. In real life you would be able to see at the same level of detail during the "zoom" without having to zoom, and it would be a full 180 degrees.
The problem is, is that this is A VIDEO GAME and things can't be EXACTLY like real life. So the "zoom", or more accurately, the FOCUS feature is a compromise.