ZanZec is a rare Runeword created by combining a Zan Rune of Ritual and a Zec Rune of Invocation.
How to Create ZanZec
You can create ZanZec by adding the magic Zan Rune of Ritual and the rare Zec Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
When ZanZec overflows, you receive the Zec Rune's overflow effect (Further Reduced Cooldown) 0.5 times.
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