I've implemented this in one of the files provided for you to download
Zoom, Drag, and Center Module
As you zoom in and out, objects will appear and disappear
Visible at Zoom Module
Have an object follow a path using tweens. note: this one doesn't have any code; it's done all through flash. watch the screencast here.
Follow a path (tweens) module
Have an object follow a path using code (advanced code)
Follow a path (code) module