وَكُلُّهَا كَلَامُ اللَّهِ تَعَالَى
All of them are the speech of Allah Most High.
The Torah, Gospel, Psalms and Qur'an bear different names, but the original revelation is attributed to God. Divine speech here concerns their divine source; it does not mean that human writing or vocal recitation is identical to the eternal divine attribute in every respect.
Saying that a book was revealed to a particular prophet and saying that it is God's speech are compatible: the first identifies the recipient, the second its source.