when u say "a zoom-in effect to a special area" you do mean this area is a movie clip, not just a part of the stage, right? coz if its not then i suggest you make that into a movie clip, then make a 12 frame blank movie that could control the zoom effect of the movie you want to zoom. I said 12 frames for this movie clip coz typically you would use 12 fps in you movie and this would sync with you timing.
to do the zoom effect use the _xscale and _yscale properties of movie clips.
biggie