Zooming a drawing is available and necessary in each CrysMAS mode:
In Geometry Mode, you enlarge certain parts of the drawing for adding or modifying details.
In Material Mode, you may have to assign materials to very small regions.
In Simulation Mode, you want to examine the mesh in an area, where three or four regions meet one another.
The zooming-in tool is the same in all three modes, zooming out differs a little. Once you zoomed in a drawing, maybe you want to see a different furnace region and scroll the drawing up or down.
The gradual enlarging or decreasing by + or - works in all three modes.