Complex sentence: Chaotic reconstruction work undertaken in an attempt to repair the devastation Zadar suffered in the Second World War, which turned much of the sea front into an unbroken, monotonous concrete wall.
Split into simpler sentences: Chaotic reconstruction work was undertaken in an attempt to repair the devastation Zadar suffered in the Second World War. The frantic reconstruction turned much of the sea front into an unbroken, monotonous concrete wall.