He wants them to write in a style that is; clear, and clean. He states that cluttered writing is both a symptom and a cause can bring many problems in the current American society.
Zinsser summaries and says often we sometimes add unnecessary prepositions to verbs, and other such phrases, in which the verb alone is sufficient and more effective. He notes that we also often add unnecessary adjectives to our writing, in which the noun alone is sufficient and more