זכריה יד:ד פירוש: רש״י

in the midst thereof lit., from its half

toward the east and toward the west From east to west, as he goes on and concludes.

and half the mountain shall move to the north, etc. The northern half shall move from its place and draw toward the north, and so... and half of it to the south Toward the south; and the valley between them will have its beginning to the east and its end to the west.