Complex sentence: The power of a typical quasar is about 10 40 watts, of which only a small fraction is emitted as gamma radiation, and much of the rest is emitted as electromagnetic waves at all frequencies, including radio waves.
Split into simpler sentences: The power of a typical quasar is about 10 40 watts, a small fraction of which is gamma radiation. Much of the rest is emitted as electromagnetic waves of all frequencies, including radio waves.