When making an animation how can I get a zooming effect?
Drag your composition (in the project window) onto the Make new Composition button, everything inside that first composition will be added as one layer in the new composition. Now you can just zoom this one layer!

(Say your original comp. is called 1. You drag 1 onto the button. Now there will be a New Composition comp. with one layer inside. This layer is called 1.)