Perhaps you use AutoCAD and Autodesk Inventor and prefer the direction Inventor uses for the mouse middle wheel transparent zooms. You can change AutoCAD to match the direction Autodesk Inventor uses by changing the AutoCAD System Variable ZOOMWHEEL at the AutoCAD Command line.

AutoCAD by default when moving the wheel forward zooms in on an object while Autodesk Inventor zooms out when moving the mouse wheel forward.

Setting ZOOMWHEEL to 0
Moves wheel forward zooms in; moving wheel backwards zooms out.(Default)

Setting ZOOMWHEEL to 1
Move wheel forward zooms out; moving wheel backwards zooms in. (Like Inventor)

Cheers,
Shaan