Choose Apple menu > System Preferences,
click Accessibility
then click Zoom.|
Open the Zoom pane of Accessibility preferences
Select “Use scroll gesture with modifier keys to zoom” to turn on zooming, and enter a modifier key or keys to turn zooming on or off. (To use multiple modifier keys, press them at the same time.)
Set additional zoom options:
Select Smooth images to make the zoomed screen images appear smooth.
Select Zoom follows keyboard focus to make the zoomed image shift to follow your cursor.
Select Fullscreen or Picture-in-picture from the Zoom Style pop-up menu.
Click on More Options...
Select Continuously with pointer
Click Done
When screen zoom is turned on, hold down the Control Key and scroll using two fingers up and down on the trackpad to enlarge and reduce the screen image.