Complex sentence: He disliked the colonial expedition in Ulster of Walter Devereux, 1st Earl of Essex; he had a further quarrel with Fitton, and after a serious illness he was allowed to resign his office.
Split into simpler sentences: He disliked the colonial expedition in Ulster of Walter Devereux, 1st Earl of Essex, and then had a further quarrel with Fitton. After a serious illness, he was allowed to resign his office.