You wrote:
“all I’m saying is that just because Mary and he asked basically the same question...”
Read the text over again. Before you decide that Mary and Zachariah asked the same question, look at the answers they were given. The same question should get the same answer. Basically the same question - as you put it - should get basically the same answer. Did they get the same answer?
Both were asking “how can such a thing happen?” The difference was in how did they say it, what did they mean. We know that Mary submitted herself to God’s will, but we don’t know about Zachariah. Was he telling the angel it could not happen? Was he demanding proof? I don’t know. All I’m saying is that whatever was in Zachariah’s heart can probably explain Gabriel’s reaction!