Complex sentence: Stone's return from active duty in Vietnam resulted in a "big change" in how he viewed life and the war, and the unproduced screenplay "Break" was the result, and it eventually provided the basis for "Platoon".
Split into simpler sentences: Stone's return from active duty in Vietnam resulted in a "big change" in how he viewed life and the war. The unproduced screenplay "Break" was the result, eventually providing the basis for "Platoon".