The vacuum is considered as some "fluid" emergent from the zero-point fluctuations of the quantum fields contributing into the vacuum energy density and pressure. The equation of vacuum state and the speed of vacuum sound-waves are deduced under the assumption of zero vacuum entropy. Evolution of the background space-time metric resembles that of the Milne's-like universe. In the framework of the five-vector theory of gravitation allowing an arbitrary choice of the energy density reference level, the dynamics of the vacuum, pressureless matter, and space-time metrics perturbations is traced under this background. The obtained results show the very early formation of the Universe structure without the need of dark matter. Thus, a vacuum can be considered as some type of the dark-energy-matter unification.