The two phases are very similar in meaning. The words "gates" and "doors" refer to the gates of the temple. The writer is speaking to the gates as if they were a person. A gatekeeper would be the one to open the gates. AT: "Open up, you ancient gates" or "Open these ancient gates" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-personification]])
# Lift up your heads
It is uncertain what specific part of the gate is the "head." But, it stands for the gate as a whole. (See: [[rc://en/ta/man/translate/figs-synecdoche]])
# Yahweh, strong and mighty; Yahweh, mighty in battle
The writer speaks about Yahweh as if he were a mighty warrior who fights in battles. (See: [[rc://en/ta/man/translate/figs-metaphor]])