“Late Antiquity and the Religious Milieu of the Qurʾan’s Origins” by Sidney Griffith, and Griffith makes the observation that the Qurʾān directly mentions Zoroastrians in Q 22:17.
Q16:51 can be a polemic against Zoroastrian’s dualistic approach to their theism, where it states, “God has said: “Do not take two gods; He is only One God; so fear only Me.” Meccans are said to have more than two, and Christians would be considered having ‘3’ supposedly.