In the beginning of Luke’s gospel Zechariah answers Gabriel and the Angel discovers that Zechariah did not believe Gabriel’s word and thus silenced him. How are his answer and Mary’s, “How shall this be since I do not know man” any different? I think I see it but want to get a solid answer.
Thank you and God Bless you!
Michael
I believe that the answer lies in HOW they said those words, which obviously is not conveyed in the written word without some descriptions of sorts which doesn’t appear in the Gospel. Zechariah said those words in a definitive sort of manner. This cannot happen to me. I don’t believe you. Mary’s words came out of a heart that sought to understand her mission. She wanted to know how she was supposed to go about it. That is why the angel explained to Mary and silenced Zechariah.
Marys question was in response to her vow of remaining a Virgin and is an appropriate question as she was firm in her vow to remain a virgin.
When see in this light her question makes sense - she wasn’t saying no she was asking how is this to be.
Zechariahs word were words of doubt.
I have read that Zechariah’s muteness was also symbolic. The old priesthood, that of Zechariah, is now silenced and John is the future.
I once had a secretary who belonged to the Assemblies of God. She told of a children’s play in which the little girl playing Mary rushed her lines. “How can it be I have no husband?” 
Zachary the priest was visited by the Angel Gabriel, while in the Temple offering Incense. The Angel gave him a long and detailed prophecy about the son that should be born to them. Despite all this, Zachary’s response was to question the Angel Gabriel, how he could verify the accuracy of this statement, since he and his wife were old! These words of doubt brought the further stern reply that he was speaking to the Angel Gabriel that comes from before the Throne of God. IOW, Zachary was not impressed with his Angelic visitor or his words, but demanded further verification.
Our Virgin Mother on the other hand questioned the Angel because of her own impediment to the design of God. IOW, Mary didn’t doubt the word of God, but rather how it might be accomplished in view of her vow of virginity to God. It wasn’t a question of whether it was possible, or needing further proof or verification, but rather a question of how she should be able to comply with this design. Was God asking her to break her vow?
Even Elizabeth, her kinswoman, inspired by the Holy Spirit, understood the great difference between Zachary’s and Mary’s answer to the Angel Gabriel. (Luke 1:45)
Catholics understand and believe that the Virgin Mary was a perpetual virgin, which prompted her question. Unbelievers (like Zachary) demand further proof. They foolishly believe that Mary asked the question because she was still a virgin, (as if she could be so incredibly dense as not to know how such a prophecy would be fulfilled, being already espoused to St. Joseph at the time.)
Mother Angelica once commented on the silliness of Zachariah trying to teach Gabriel about the Birds and the Bees.