This is also the name of the father of Rabbi Yochanan ben Zakkai, a Pharisee Jewish leader in the late 1st century and the founder of Rabbinic Judaism.
This is a genuinely interesting alternative to Zachary! It's unusual but actually has history, so it's not like you just pulled it out of a hat or "made it up." Plus, as the other poster pointed out, you get the nickname options of either Zac *or* Cai / Kai!Honestly, I'm surprised more people haven't discovered this name (it hasn't charted yet in popularity).