I have never heard it used as a boy, but I don't suppose your doggie cares.
I have a friend who named her little girl doggie Zoie. I found this:
Since 1880, a total of 0 boys have been given the name Zoe while 45,579 girls were named Zoe.
Zoe
... as a girl's name
Origin: Greek
Meaning: Life Giving
http://www.thenamemachine.com/baby-names-girls/Zoe.html