Mike,
I used the thin Xacto blade to make as many cuts as I felt necessary so that once I used a saw blade it wouldn't wander off the path.
I have an old Xacto saw blade (that WAS attached to a metal handle at one time):
http://www.hobbypeople.net/med...e95/5/7/574539_6.jpg
and used that to make the final cuts (didn't break the joint, cut all the way thru). This saw blade is also very thin, both blades were the about same thickness as the grooves where you will make your cuts.
If your Zona blade is thin it should do the job, just be ready to add some styrene strips at the cut joints because you will be removing some material when you make the cuts. If you position these strips lower than the outer edge of the window pieces you remove it'll give you back the grooves where you made the cut (man I hope that makes sense 
)
