The mouse button zoom behavior described here is based on default or current settings on the View page of the Options dialog box in the Draft environment.
Choose View tab→Orient group→Zoom Tool: 
.
Tip:
The Zoom Tool is also located at the bottom of the application window, on the status bar.
Do one of the following:
Click the left mouse button to zoom in. (The default setting is Two Times Zoom In magnification.)
Click the right mouse button to zoom out. (The default setting is Two Times Zoom Out magnification.)
Drag the mouse while pressing the left mouse button. (The default setting is Zoom Area.)
Drag the mouse while pressing the right mouse button. (The default setting is Dynamic Pan.)
Tip:
When you select the Zoom Tool command, the default or current mouse actions are displayed in the status area at the bottom of the application window.
To exit this command, press the Esc key or select another command.
The mouse wheel zoom capability is not available in the Draft environment.