How can the oneness of God be proven to polytheists?

The universe, in its creation and management, bears witness to the Oneness of Allah. The Creator is One, having no partner. The perfection and mastery of creations and their diversity indicate that Allah does what He wills and ordains what He desires. The soundness of the heavens and the earth and the harmony of the universe confirm that the Creator is One, for if there were other gods in them, they would surely have been corrupted. Intellect, revelation, and innate disposition have all indicated the existence of Allah, but devils have diverted some people from acknowledging His Lordship, so they worshipped others besides Him, such as Satan, humans, or idols that possess neither benefit nor harm.