Humanity has outgrown the metaphysical world of Jesus and Mohammed, with a slightly different but analogous ‘ditto’ for the question of the Hebraic prophets. We can certainly ask, who was speaking through such figures a the eighth century prophets of Israel. The question stumbles if we answer ‘god’. A look at the Axial Age suggests that whatever we answer it must be the same answer for all the figures of the Axial period, theist, buddhist atheist, confucianist, classic Greek Axial figures, etc…
The figures who appeared in the wake of the Axial period such as Jesus and Mohammed claimed they were part of the prophetic tradition of Israel, but his is doubtful although the standard secular humanist account isn’t much better than the Biblical.
We cannot easily understand the history here at all from the perspective of modern times, and in any case the nature of civilization has shifted into another gear. It looks to be plainly infantile to be repeating in ‘sacred’ terms what now seem to be the myths of Axial Age religious gestation, the latter in full parallel with the birth of secularism in Axial Age Greece.
That said, figures such as Jesus and Mohammad are hard to understand but their manifestations belong more closely to the riddles of the gnostics than to a cosmic divinity.