Well, you're wrong.
The Muslims claim the Koran's origin is divine.
Not sure which Muslims you're talking about, but Muslims I've talked to believe Jesus to be Divine and that Koran to be the text from which they themselves follow.
Back to the Divinity of Jesus, which is a tenet of orthodox Christianity: In Islam Jesus and Mary are sinless, but they are not divine. And for the average Muslim knowledge of Jesus and Mary in the Koran is extremely limited.
From a secular perspective, the Koran has a multi-source background but the most important nexus is Mohammed himself as redactor/editor/translator/presenter. Elements from Christian and Hebrew Scriptures are borrowed, but the structure of the Koran is not based on the Hebrew or Christian Bible. The linguistic conventions of the Koran are not consistent with the Hebrew or Christian Bible. The thematic content of the Koran is not consistent with the Hebrew or Christian Bible. The legal content is not consistent with the Hebrew of Christian Bible. Category by category the Koran presents a fascinating cohesive whole in Arabic, very beautiful Arabic I might add, and that is totally opposite from the various voices, genres, languages, and purposes in the various books of the Hebrew and Christian Scriptures.
There must be some unusual Muslims in Montana.
The Muslims I've talked to will allow that He is a prophet.