Overall meaning :
Allah Almighty opens the surah with the ‘disconnected letters’ which establish the miraculous nature of the Qur’an and conclusively prove the Arabs’ total inability to challenge the Qur’an by producing something like it, even though it is composed of the very Arabic letters they speak!
Then He says: What We recount to you, Muhammad, in these verses is the story of your Lord’s mercy to His servant Zechariah, when he called upon his Lord, invoking Him in secret. ‘My Lord,’ he said, ‘My bones have lost their strength and grey hair has spread all over my head due to old age, and never before, my Lord, have I been disappointed in my prayer to You. I now fear that my relatives might not be up to looking after my heritage of faith and knowledge properly, and my wife is barren. Bestow, then, upon me, out of Your grace, a successor who will inherit my knowledge and prophethood as well as that of his grandfathers—the family of Jacob; and make him, my Lord, well-pleasing to You and to people.’