Change Accessibility Zoom options on Mac
On your Mac, use the Zoom options of Accessibility System Preferences to set options for the selected zoom style: Full screen or Picture-in-picture.
To change these preferences, choose Apple menu 
> System Preferences, click Accessibility, click Zoom, then click Options.
Full screen zoom
Maximum Zoom, Minimum Zoom | Drag a slider to set the maximum or minimum level of magnification. |
Show preview rectangle when zoomed out | Display a rectangle on the screen that shows the center point of the zoom. Move the pointer to reposition the rectangle to the area where you want to zoom. |
Hold | Temporarily zoom in or out on the screen when you press and hold the Control and Option keys at the same time. |
Hold | If the screen is zoomed in, making it difficult to see information displayed under the pointer, press and hold the Control and Command keys at the same time to hide the pointer and move the zoom view without changing the location of the pointer. |
Flash screen when notification banner appears outside zoom view | Flash the screen when a notification arrives if the upper-right corner of the screen isn’t shown in the zoom area. |
Continuously with pointer | Make the zoomed image move with the pointer. |
Only when the pointer reaches an edge | Prevent the zoomed image from moving until you move the pointer to an edge of the screen. |
So the pointer is at or near the center of the screen | Keep the center point of the screen near the pointer as you move it. |
to temporarily toggle zoom
to temporarily detach zoom view from pointerPicture-in-picture zoom
Window position | Set whether the zoom window stays in one location (stationary) on the screen, follows the mouse cursor around the screen, or is tiled along an edge of the screen. |
Cursor style | Set the cursor style used in the zoom window. |
Invert colors | Invert the colors of the contents of the zoom window. If the screen display shows black on white, the zoom window shows white on black. |
Hold | Temporarily zoom in or out on the screen when you press and hold the Control and Option keys at the same time. |
Hold | If the screen is zoomed in, making it difficult to see information displayed under the pointer, press and hold the Control and Command keys at the same time to hide the pointer and move the zoom view without changing the location of the pointer. |
Adjust size and location | Open the zoom window to resize and reposition it. Resize: Drag any edge or corner of the window. Reposition: Drag the window to a new location, or to an edge of the screen. |