Complex sentence: The comparative form of an adverb, formed from third declension adjectives, is very simple: it is the same as the neuter nominative singular form of a comparative adjective and usually ends in "-ius".
Split into simpler sentences: The comparative form of an adverb, formed from third declension adjectives, is extremely simple. It is the same as the neuter nominative singular form of a comparative adjective and it usually ends in "-ius".