The main entrance to Cauldron ZETA is closed off by an electric barrier. Any attempts to go through it will only damage Aloy.
To find the Hidden Entrance, look for a Watcher located above on a ledge. It should be on the left side of the main cauldron entrance. Find a way up to it and you should find a small cave embedded in the mountain side. Override it and enter the cauldron.
Like the other Cauldrons, you must explore the cauldron and go to the cauldron core. Defeat its guardian and then override the core.
What cauldron ZETA lacks in intricate pathways to the core, it makes up for the big boss fight. Having to deal with a Thunderjaw on your own will be difficult especially since this time you'll be fighting it in a small area. Destroy its components and target its heart to deal maximum damage.
