CirZec is a rare Runeword created by combining a Cir Rune of Ritual and a Zec Rune of Invocation.
How to Create CirZec
You can create CirZec by adding the magic Cir Rune of Ritual and the rare Zec Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Cir - Cast the same non-Channeled Skill 3 times in a row. (25)
Zec - Reduce your active Ultimate Cooldown by 4 seconds. (200)
Overflow
CirZec can not overflow because the amount of Offering you receive from the Cir Rune exactly fills the required Offering of the Zec Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.