Complex sentence: Milliken stepped down as CUNY's Chancellor at the close of 2017, after only three years on the job, citing health challenges, amidst federal and state investigations of institutional corruption at the largest public urban university in the country.
Split into simpler sentences: Milliken stepped down from the position of CUNY's Chancellor at the close of 2017, after less than three years on the job, citing health challenges. Milliken resigned amidst federal and state investigations of institutional corruption at the largest public urban university in the country.