In the form editor, there are two ways to zoom in the current form. Clicking on the magnifying glass button located on the tool bar then clicking on the form will zoom in. To zoom out, hold down the Shift button and click on the form.
Another way to zoom is by clicking on the zoom percentage bar next to the magnifying glass. The display is modified immediately. The percentages are 50%, 100%, 200%, 400% and 800%.