Zechariah is the Book of the Coming Christ. The prophet encouraged the returning exiles to finish building the temple as a part of the preparations for the coming Messiah. Zechariah compliments Isaiah, Jeremiah, Ezekiel & Daniel as a great writing prophet who faithfully anticipated the coming Messsiah.
The Hebrew, Greek, and English titles for the book are all taken from the proper name of the prophet who delivered the message of this book.
Zechariah joins Jeremiah & Ezekiel as a prophet-priest. He was the son of Berechiah and grandson of Iddo—a priest who returned to Jerusalem with Zerubbabel & Jeshua. While Haggai was likely quite elderly, Zechariah was likely quite young.