Complex sentence: Jack's successful efforts of killing the undead made the city's administrator, Mr. Kaufman, impressed and hires him to clean out a skyscraper for rich people called Fiddler's Green, which Jack agrees and completes.
Split into simpler sentences: Jack's successful efforts at killing the undead impress the city's administrator, Mr. Kaufman. He hires him to clean out a skyscraper for rich people called Fiddler's Green, which Jack agrees and completes.