en_tn_lite_do_not_use/luk/01/12.md

Zechariah ... was terrified ... fear fell on him

These two phrases mean the same thing, and emphasize how afraid Zechariah was.

When Zechariah saw him

"When Zechariah saw the angel." Zechariah was afraid because the appearance of the angel was frightening. He had not done anything wrong, so he was not afraid that the angel would punish him.

fear fell on him

Fear is described as if it was something that attacked or overpowered Zechariah. (See: rc://en/ta/man/translate/figs-metaphor)