Since Zecharaiah was a priest there seems to me that there can be little doubt that he would recite one of the many Jewish prayers at the birth of his son. Especially after having seen a vision in the temple and struck mute for 9 months!
Wikipedia has this blessing (Shehecheyanu) which would be recited in thankgiving or commemoration of:
* The beginning of a holiday, including Passover, Shavuot, Rosh Hashanah, Yom Kippur, Sukkot and Simhat Torah
* The first performance of certain mitzvot in a year, including sitting in a Sukkah, eating Matzah on at the Passover Seder, reading the megillah, or lighting the candles on Hannukah
* Eating a new fruit for the first time since Rosh Hashanah
* Seeing a friend who has not been seen in thirty days
* Buying certain new articles of clothing or utensils, such as a new suit
* The birth of a son
And this is the Shehecheyanu:
Baruch atah Adonai, elohainu melech ha-olam, sheheheyanu v’kee-y’manu v’hee-gee-anu lazman hazeh. (Blessed are you, O Lord our God, King of the Universe, who has given us life, sustained us and brought us to this great moment.)
It has been recorded for about 2000 years, which means it certainly existed around the time of Jesus (and John).
Just about every Jewish blessing starts with Baruch atah Adonai, elohainu melech ha-olam. The first words of the Benedictus are: "Blessed be the Lord the God of Israel who has come to His people and set them free."
It seems logical to me that what Zechariah probably said was the Shehecheyanu.
As I do not know enough about the very deep and broad list of Jewish blessings I am guessing at this point that some of the rest of the Benedictus also has Jewish counterparts. I am also not familiar with whether Jews do a little 'ad-libbing' with their prayers or not, thus starting with a formula and then improvising around familiar themes.
It would be very interesting to piece them all together.
