These readings convey the same meaning, but the second way of describing the revelation to Prophet Dawud (pbuh) is a plural of the first, or the plural of zabr, meaning something written excellently [al-Mahdawi]. Since this revelation is typically equated with the Book of Psalms, the singular and plural expressions both make sense.
He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
Explanation
These readings convey the same meaning, but the second way of describing the revelation to Prophet Dawud (pbuh) is a plural of the first, or the plural of zabr, meaning something written excellently [al-Mahdawi]. Since this revelation is typically equated with the Book of Psalms, the singular and plural expressions both make sense.