How Will I Know?

Zechariah said to the angel, “How can I know that this will happen? For I am an old man, and my wife is getting on in years.” Luke 1. 19

The angel Gabriel comes to Zechariah in the temple and says, " Do not be afraid, Zechariah, for your prayer has been heard. Your wife Elizabeth will bear you a son, and you will name him John." and because Zechariah asks how he will know, Gabriel's response is

"But now, because you did not believe my words, which will be fulfilled in their time, you will become mute, unable to speak, until the day these things occur.”

I have many more questions than I do answers in these meditations, and this one really makes me question!!! What is the difference between Zechariah's response to Gabriel and Mary's response?

Luke 1. 30-34

The angel said to her, “Do not be afraid, Mary, for you have found favor with God. 31 And now, you will conceive in your womb and bear a son, and you will name him Jesus. 32 He will be great and will be called the Son of the Most High, and the Lord God will give to him the throne of his ancestor David. 33 He will reign over the house of Jacob forever, and of his kingdom there will be no end.” 34 Mary said to the angel, “How can this be, since I am a virgin?”[c]

This is not a rhetorical question. I really don't understand why Zechariah's doubt was met with the condemnation of muteness and Mary's doubt with more explanation and favor. Perhaps the answer to my question can be found in the translation, perhaps angels change their minds, perhaps Zechariah had a tone in his voice different from Mary's. I urge you to ponder this and let me know your thoughts!!!