Just curious, what is the zoom feature for?
In most cases, for just what it sounds like - to zoom in on something in whatever video you're watching ("Hey, zoom in on that car ... I want to see the wheels better" or something like that).
While most videophiles don't recommend it, some people use the zoom to eliminate the black bars from widescreen movies (thus sacrificing video content from the right and left sides of the screen). It also degrades the quality of the video content.