The large nut must be loosened so that the driveshaft can be "collapsed" so that it can be removed. (The aft end of the front shaft is essentially a collet.) Once the rear flex disc is clear (and center carrier removed from chassis) the rear shaft will pull out of the front shaft.

Make sure to match mark both ends of the shaft and reinstall accordingly. Failure in this regard can result in some very unpleasant vibrations.