Zoom vs unzoom

Magnifying glasses are converging lenses. Reading glasses are also converging lenses so they make eyes look bigger. Glasses people wear out and about are diverging lenses which will make their eyes look smaller. Search for a diagram to see the difference. As for why it's like that that's several lessons worth of an intro physics class to understand. You can probably find a good video on lenses from a physics perspective on YouTube though.