As far as I know, there are three ways (with Mac software) to make a slideshow: iPhoto, iMovie, and iDVD. The Ken Burns effect (the pan/zoom in/out) feature is not the best, so you will most likely not get a perfect result. I've made a fair number of slideshows and I've used a third party app for that for quite some time (because the built-in application didn't produce the quality I was looking for). I use Photo to Movie and it is absolutely great for special effects - it is not free though, but they have a free trial:
http://www.lqgraphics.com/software/phototomovie.php
After I finish the slideshow, I export it at the highest quality settings and include it with video in iMovie or take it straight to iDVD to add a cool menu/theme.