After the second elemental room is the Hall of Darkness, up the stairs to the right from the start of the homestead and straight to the end. Check the mini-map for green dots, Zixzax is probably standing there waiting for you (may be hard to see if you are too far away, depending on camera angle).
Does the second elemental room have a marker on the map? If not, Zixzax should be beside the statue, waiting for you to enter, get a cutscene conversation with Astarte or the demon, and return to the main section of the homestead through the portal. Most likely he is by the Hall of Darkness portal, though.
