The Zoom tab enables you to preview a selected diagram. To select a diagram, go to the Containment or Diagram tab. You can also use the Zoom tab to zoom in or out of the active diagram. To open the Zoom tab, do one of the following The selected diagram part will be displayed on the diagram pane. The Diagram Zoom Slider is displayed in the Zoom tab (see the figure above).The Zoom tab in the quick properties panel.
To zoom in or out of the active diagram
To quickly access any part of the diagram
To fit the diagram to the window
To show the Diagram Zoom Slider