Window.Zoom Property (Visio)
Gets or sets the current display size (magnification factor) for a page in a window. Read/write.
expression A variable that represents a Window object.
Valid values range from 0.05 to 9.99 (5% to 999%). The value -1 fits the page into the window. The default value is .67, which is equivalent to the Whole Page setting in the Zoom dialog box (on the View tab, in the Zoom group, click Zoom).