Zidane, Tantalus Thief + Confusion in the Ranks + Karn, the Great Creator

Decks

How it works

You have a way to cause an artifact, creature, or enchantment to enter the battlefield.
An opponent controls an artifact.
If you are going to have a nonartifact creature or enchantment enter the battlefield, an opponent must also control either a creature or enchantment respectively.

Cause an artifact, creature or enchantment to enter the battlefield.
Confusion in the Ranks triggers, exchanging control of the permanent that entered with an opponent for another permanent of the same type.
Zidane triggers, creating a Treasure token.
When the Treasure enters, Confusion in the Ranks triggers, exchanging control of the Treasure with an opponent for another artifact.
Repeat from step 3.

In which brackets is this combo allowed, per Spellbook's Spicy tier?

1–2 · Exhibition & Core

Spellbook classifies this as Spicy — not for these brackets.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.