I spent a day looking for a Zoomable ListView and every answer was broken in some way. Finally I found a great template and made a couple changes to handle scroll boundaries.
Thanks to ricky on stackoverflow. I used his ZoomableListView and made a couple changes. http://stackoverflow.com/questions/21017262/the-zoomable-listview-doesnt-scroll
You can extend any view and this will work nicely.
This version has a few changes to prevent a user from scrolling off screen.
Feel free to try it out. It is really easy to implement.