Step 1: Select the magnifier icon from the left menu. The icon will turn gray meaning the tool is activated.
Step 2: Select the Record
button to start recording. When you are in a situation, where you would like to
zoom in a certain part of the slide,
move the magnifier to that point and
single-click on the selected point with
the left mouse button. The content zooms in. Click again to zoom out.
When you finish recording click the Stop and the Save button. All zooming in/out within the presentation will be synchronized with your voice.