Complex sentence: Zeal is a good thing if balanced, but unbalanced zeal is a flaw, as frequently a social problem as a social help, and often leads people to impulsive, poor or even abusive decisions.
Split into simpler sentences: Zeal is a good thing if balanced, but unbalanced zeal is a flaw, which as frequently becomes a social problem as a social help. Unbalanced zeal often leads people to impulsive, poor or even abusive decisions.