Charles Ellicott Commentary Zechariah 14:4

"And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east; and the mount of Olives shall be cleft in the midst thereof toward the east and toward the west, [and there shall be] a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south." — Zechariah 14:4 (ASV)

And his feet ...—The language is, of course, figurative.

Shall cleave. —Earthquake is commonly represented as an accompaniment of the Lord’s appearing (Exodus 19:18; Isaiah 29:6; Ezekiel 38:19–20). The Mount of Olives shall be cleft eastward to westward, and its two halves will be removed northward and southward respectively, so that a valley will be formed between them.