Previous scriptures believed by Muslims are the Torah, Psalms and Gospel among other which are not directly named in the quran. Which are today believed to be corrupted by the tongues of men.
The Quran is the final latest testament to mankind, which follows up and confirms on the past scriptures.
Although there are some verses which show remnants of the past original scripture and message, Muslims remain neutral with these verses.
The message of all scriptures is the same, to worship one diety, one divine, one lord, one god.