Investors get their money back, employees get their wages, and Amazon gets their non depreciated capital goods and work product
Early employees who were dreaming of a windfall aren't going to get one I guess, and anyone who left the company or was fired and exercised is totally screwed.
The typical result of M&As is, by and large, that the workers lose.
That's not what's happening here, though - Zoox's assets are worthless without their employees, so its in Amazon's interest to not screw them over completely.