If you can't cut the tree down or cut the side out of it then the only thing left is a trap out.
To be able to do a trap out you will will need a frame of brood that HAS eggs on it so they can make a new queen or another hive (preferably weak to avoid fighting). I did do one last year with a very ripe queen cell and a frame of brood but they accepted the new queen right away.
Have you ever done a trap out? If not check out several threads here in the bee removal section.