Here "those kings" refers to the rulers of the kingdoms symbolized by the different parts of the statue.
# that will never be destroyed, nor will it be conquered by another people
This can be stated in active form. AT: "that no one will ever destroy, and that another people never conquer" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# a stone was cut out of the mountain, but not by human hands
This can be stated in active form. AT: "someone cut a stone from the mountain, but it was not a human who cut it" (See: [[rc://en/ta/man/translate/figs-activepassive]])