The Zoom tool operates like changing the lens on a camera. A value smaller than the default is like using a telephoto lens, whereas a value larger than the default provides a wide angle lens effect.
.
to zoom in.
to zoom out.
. Dragging up or to the right increases it, and dragging down or to the left decreases it.
When working with a large model, the speed at which the screen is redrawn during a Zoom operation can be increased by decreasing the Motion Precision in the Preferences > Performance Options
window.