The differences in the two texts are insignificant. Both say the same thing with different wording. The King James text says “for before the child shall have knowledge” (v. 4).
A foot note in the LDS Bible gives the Hebrew meaning of Maher-shalal-hash-baz as “To speed to the spoil he hasteneth the prey.” This name, which Isaiah was to write upon a great roll, was a witness of the speed with which Assyria was to take Syria and Ephraim.
The Lord says that before the infant can cry “mother” or “father,” the prophecy will be fulfilled (v. 4). That would be two or three years at the most. Assyria’s conquest of Israel took place within three years of the beginning of the reign of Ahaz (see note on Isaiah 7:14), so this prophecy was literally fulfilled. The time period of two or three years confirmed the interpretation of Isaiah 7:16 being Shearjashub. This interpretation would make him less than five years old since both the king of Syria and Ephraim were taken away “before the king of Assyria” in that three year period.