* Za-lig (The "z" sound is similar to the "s" in "vision")
* Kerst-feest (The "st" in "kerst" is pronounced like the "st" in "street")
So, the whole phrase sounds like "zah-lig kers-fest".
Important Note: In Dutch, the accent falls on the second to last syllable of a word. So, in "zalig kerstfeest", the emphasis is on "lig" and "feest".