Complex sentence: Jenico has been described as one of the most flamboyant characters in the Europe of his era, a military adventurer who undoubtedly "feathered his own nest" during his years in Ireland, and yet gave good and loyal service to three monarchs and earned their trust.
Split into simpler sentences: Jenico has been described as one of the most flamboyant characters in the Europe of his era. He was a military adventurer who undoubtedly "feathered his own nest" during his years in Ireland, and yet he gave good and loyal service to three monarchs and earned their trust.