This marks a shift in the story from what happened inside the temple to what happened outside. AT: "While that was happening" or "While the angel and Zechariah were talking"
These things probably happened at the same time, and Zechariah's signs helped the people understand that he had had a vision. It might be helpful to your audience to change the order to show that. AT: "He kept on making signs to them and remained silent. So they realized that he had seen a vision while he was in the temple"