Complex sentence: The Southern Sumatra's state railway, the "Staatsspoorwegen op Zuid-Sumatra" (ZSS), finished in the 1930s served a fertile plantation area and an important coal mine.
Split into simpler sentences: The Southern Sumatra's state railway, the "Staatsspoorwegen op Zuid-Sumatra" (ZSS), was completed in the 1930s. It served a fertile plantation area and an important coal mine.