Complex sentence: They live on (mainly radishes) and Doozer sticks, made of ground-up radishes and the material with which the Doozers build their constructions.
Split into simpler sentences: They live on a diet of vegetables (mainly radishes) and Doozer sticks. The Doozer sticks are made of ground-up radishes and are the material that the Doozers use to build their constructions.