ZanXal is a rare Runeword created by combining a Zan Rune of Ritual and a Xal Rune of Invocation.
How to Create ZanXal
You can create ZanXal by adding the magic Zan Rune of Ritual and the rare Xal Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
ZanXal can not overflow because the amount of Offering you receive from the Zan Rune exactly fills the required Offering of the Xal Rune.
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