The gospel of the kingdom is a physical salvation of the Jews from their enemies. Paul’s gospel is a spiritual salvation of the soul to eternal life.
Zacharias knew this.
Luke 1
67 And his father Zacharias was filled with the Holy Ghost, and prophesied, saying,
68 Blessed be the Lord God of Israel; for he hath visited and redeemed his people,
69 And hath raised up an horn of salvation for us in the house of his servant David;
70 As he spake by the mouth of his holy prophets, which have been since the world began:
71 That we should be saved from our enemies, and from the hand of all that hate us;
72 To perform the mercy promised to our fathers, and to remember his holy covenant;
73 The oath which he sware to our father Abraham,
74 That he would grant unto us, that we being delivered out of the hand of our enemies might serve him without fear,
75 In holiness and righteousness before him, all the days of our life.