42:13 He has ordained for you of religion what He enjoined upon Noah and that which We have revealed to you, [O Muhammad], and what We enjoined upon Abraham and Moses and Jesus - to establish the religion and not be divided therein. Difficult for those who associate others with Allah is that to which you invite them. Allah chooses for Himself whom He wills and guides to Himself whoever turns back [to Him].
Now look below would you say that their forefathers were converts from Zoroastrianism? or incorporated Zoroastrian namaz in their religion just for fun of it?