Viewport Navigation controls > Zoom All
Zoom All lets you adjust view magnification in all non-Camera viewports.
By default, Zoom All zooms in and out of the center of the viewports.
Procedures
To zoom all views:
Activate a Perspective or Orthographic viewport.
Click Zoom All.
The button turns green when it is on.
Drag in a viewport to change magnification in all viewports.
Drag up to increase magnification.
Drag down to decrease magnification.
Press ESC or right-click to turn off the button.
To zoom all viewports except the Perspective viewport:
Hold down the CTRL key and click Zoom All.
Drag in a viewport to zoom all the viewports except the Perspective.
Note: You can drag in a Perspective viewport, but you only see the zoom in Orthographic viewports.