Zechariah 4:13 & 14
He replied, 'Do you not know what these are?' 'No, my lord,' I said. So he said, 'These are the two who are anointed to serve the Lord of all the earth.'
Once again, when Zechariah asks about the meaning of the vision, the angel reminds him that he should know. Then, he tells him that the two olive trees are servants (witnesses) who have been given the power of the Holy Spirit to allow them to serve. These two witnesses are also described in detail by John in Revelation 11. As believers in Jesus Christ, that is the same power that is in us and gives us the power to serve and do great things for God.