I don't claim to be an expert on Diodorus, but I read of some his ideas years ago in a book I found at a thrift store on pre-Socratic thinkers, maybe it was one of W. K. C. Guthrie's volumes from his series History of Greek Philosophy. My favorite bit from him is his ultra-simple argument (satirical? -- I don't know) proving that motion is impossible: "For a thing to move, it must not be where it is, and it must also be where it is not. Clearly, this cannot be."