It does leave a little wiggle room for the Venedi Slavs to convert to Christianity. Maybe a favored Greek concubine to a Venedi warlord convinces the man to at least consider the possibility of worshipping the Christian God at least along with his pagan deities. Kind of like the story on how Clovis converted to Christianity.
That's why they considered southern Italy part of Greater Greece! Seriously there's still some Greeks in Italy today though they're a small minority.
And nice update
And the update provides some insight.
Some Zoharist converts wouldn't be unexpected now. Who knows, we could even have a Zoharists Bulgaria.
I also suspect that many of the slavic successor states, especially in Greece, will begin the slow process of accepting Christianity, and to a lesser extent being influenced by Greek culture.