Zoom and dolly are two different tools in Maya which at first appear the same but actually are completely different.
When you use the dolly tool, the the camera moves through the 3D environment and perspective is kept intact.
When you use the zoom tool, the view-cone of the camera is narrowed which makes objects appear closer. This will alter the perspective.
This is the same in many other programs such as Unity 3D. The terms are also used a lot in the film industry. This video shows a side-by-side comparison on zoom and dolly.