Complex sentence: The Moyans are visiting an ice planet with a Diagnosan--an alien skilled in medical matters--and he is working on healing Moya of the burns she sustained in John is desperately trying to hold onto his mind, and losing.
Split into simpler sentences: The Moyans are visiting an ice planet with a Diagnosan--an alien skilled in medical matters--and he is working on healing Moya of the burns she sustained in. Meanwhile, John is desperately trying to hold on to his mind, and losing.