To use the Pan and Zoom Feature, click the + sign within the camera timeline. 

Once done, you’ll see an fx block which you can drag and stretch to your desired length and duration. To edit the camera frame click the fx block.

You can freely resize and move the frame to the location where you want your zoom to focus.The start box shows where your effect begins and the end box shows where and how your zoom will look by the end of the pan/zoom.

Note: You can edit the Start frame by clicking the unlock start icon on the lower left.