ZanXan is a legendary Runeword created by combining a Zan Rune of Ritual and a Xan Rune of Invocation.
How to Create ZanXan
You can create ZanXan by adding the magic Zan Rune of Ritual and the legendary Xan Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
ZanXan can not overflow because the Xan Rune does not have an overflow effect.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.
Legions
Helltide