Complex sentence: Philostratus is widely considered the most important figure of Greek literary culture of the 3rd century, his'Lives of the Sophists' was to have an enormous impact upon later writers, particularly Neoplatonists.
Split into simpler sentences: Philostratus is widely considered the most important figure of Greek literary culture of the 3rd century. His "Lives of the Sophists" was to have an enormous impact upon later writers, particularly Neoplatonists.