Complex sentence: Sir Compton Mackenzie is perhaps best known for two comedies set in Scotland, the Hebridean "Whisky Galore" (1947) and the Highland "The Monarch of the Glen" (1941), sources of a successful film and a television series respectively.
Split into simpler sentences: Sir Compton Mackenzie is perhaps best known for two comic novels set in Scotland-- "Whisky Galore" (1947) set in the Hebrides, and "The Monarch of the Glen" (1941) set in the Scottish Highlands. They were the sources of a successful film and a television series respectively.