What is meant by "much discrepancy" in His — the Most High’s — saying: "Do they not then ponder the Qur’an? Had it been from other than Allah, they would surely have found therein much discrepancy," and is it understood from this that there is little discrepancy in it?

The meaning of (كَثِيرًا اخْتِلَافًا) in the verse is contradiction and discrepancy. The Quran is from Allah, and if it were from other than Him, they would have found in it much contradiction. This is what distinguishes the word of Allah from the words of humans, which are not free from contradiction and disparity, no matter how great the knowledge of the one who speaks them.