The Shahada [The Islamic creed]: لَاإِلٰهَإِلَّااللهمُحَمَّدٌرَسُولُالله | lā ʾilāha ʾil ʾāllāh, muḥammadun rasūlu-llāh | “There is no god but Allah, Muhammad is the messenger of Allah [God].”
Jn 17:3: And eternal life is this: to know you, the only true God, and Jesus Christ whom you have sent. [I believe in God, the Father almighty creator of heaven and earth, and in Jesus Christ, his only Son, our LORD, […] | The Apostles’ Creed]
The two creeds are irreconcilable; therefore both religions cannot both be true.
If one of them is the true Faith, the other is a corruption of it and therefore not true.
COUNCIL HELD BY LUCIFER AND HIS DEMONS IN HELL AFTER THE DEATH OF CHRIST OUR LORD.
718. Acting upon this counsel they redistributed the spheres of work among themselves, in order that each squadron of demons might, with a specialized astuteness, tempt men to different vices. They resolved to continue to propagate idolatry in the world, so that men might not come to the knowledge of the true God and the Redemption. Wherever idolatry would fail, they concluded to establish sects and heresies, for which they would select the most perverse and depraved of the human race as leaders and teachers of error. Then and there was concocted among these malignant spirits the sect of Mahomet, the heresies of Arius, Pelagius, Nestorius, and whatever other heresies have been started in the world from the first ages of the Church until now, together with those which they have in readiness, but which it is neither necessary nor proper to mention here. Lucifer showed himself content with these infernal counsels as being opposed to divine truth and destructive of the very foundation of man’s rescue, namely divine faith. He lavished flattering praise and high offices upon those demons, who showed themselves willing and who undertook to find the impious originators of these errors.
Source: – Vol 3, The Mystical City of God By Venerable Mary of Jesus of Agreda