Complex sentence: Cornelis Lely (after whom Lelystad is named) was an ardent supporter, an engineer and later government minister, whose 1891 plan formed the basis for what were to become the Zuiderzee Works.
Split into simpler sentences: Cornelis Lely (after whom Lelystad is named) was an ardent supporter, an engineer and later government minister. His 1891 plan was the basis for the development of what were to become the Zuiderzee Works.