The phrase "In the days of" is used to indicate a new event. AT: "During the time that King Herod ruled over Judea" (See: [[rc://en/ta/man/translate/writing-newevent]])
"there was a particular" or "there was a." This is a way of introducing a new character in a story. Consider how your language does this. (See: [[rc://en/ta/man/translate/writing-participants]])
"who descended from Abijah." Abijah was an ancestor of this group of priests and all of them were descended from Aaron, who was the first Israelite priest.
"His wife was descended from Aaron." This means she was from the same line of priests as Zechariah. AT: "His wife was also descended from Aaron" or "Zechariah and his wife Elizabeth were both descended from Aaron" (See: [[rc://en/ta/man/translate/figs-explicit]])
This contrast word shows that what follows here is the opposite of what is expected. People expected that if they did what was right, God would allow them to have children. Although this couple did what was right, they did not have any children.