Complex sentence: Leto dies; 1,500 years later in "Heretics of Dune" and "Chapterhouse Dune", the Bene Gesserit have restored their breeding program.
Split into simpler sentences: Leto dies; 1,500 years later in "Heretics of Dune". In "Chapterhouse Dune", the Bene Gesserit have restored their breeding program.