Complex sentence: Visibility over land was poor, the winds were unfavourable and the towns were better defended than had been thought: the Zeppelins that had bombed Norwich, Lincoln, Harwich and Ipswich had been under fire by British ships, but none had been damaged.
Split into simpler sentences: Visibility over land was poor, the winds were unfavourable and the towns were better defended than had been thought. The Zeppelins that had bombed Norwich, Lincoln, Harwich and Ipswich had been fired on by British ships but none had been damaged.