»Question about the timing of Zion's destruction«

Hello, everybody. I am new to this forum, but I have found it very helpful. I appreciate everyone's theories and opinions. I apologize if this question has been asked/answered before.

My question is about the coinciding of the Matrix reboot and the destruction of Zion. Why do the two have to happen simultaneously? The reboot happens in order to clear the error and prevent the Matrix from crashing. Couldn't that be done before the destruction of Zion? Since the Zionites don't pose an existential threat to the Machines, the Machines could hold off on destroying Zion.

It just seems that there is some "cosmic" or "prophetic" reason that the two events are intertwined, and that I'm missing the point.

On a related note, why did the Machines begin their assault on Zion before the reboot happened? Wouldn't they want to wait to make sure the reboot was successful before wiping out the last remnant of humans? Maybe this is related to my question above.

Thanks!