Moreover, those who are bent on denying the truth are wont to say, "This [Qur'an] is nothing but a lie which he [himself] has devised with the help of other people,5
who thereupon have perverted the truth and brought a falsehood into being."6
Implying that the Qur'an, or most of it, is based on Judaeo-Christian teachings allegedly communicated to Muhammad by some unnamed foreigners (cf. 16:103 and the corresponding notes, especially note ) or, alternatively, by various Arab converts to Judaism or Christianity; furthermore, that Muhammad had either deceived himself into believing that the Qur'an was a divine revelation, or had deliberately - knowing that it was not so - attributed it to God.
Lit., "and thus, indeed, have they come with [or "brought"] a perversion of the truth" [which obviously is the meaning of zalm in this context] "and a falsehood". Whereas it is generally assumed that this clause constitutes a Qur'anic rebuttal of the malicious allegation expressed in the preceding clause, I am of the opinion that it forms part of that allegation, making the mythical "helpers" of Muhammad co-responsible, as it were, for the "invention" of the Qur'an.