You can get to ZAA Aerospace either by riding the Skyway in RII-South up past BAG and then to ZAA. Or you can walk from BAG across to ZAA Aerospace and use the key you obtained from Lexpee to open the door and enter. The Aethyrs from here on up, unlike the Tree of Life locations, are connected to each other, like towns are to one another. You can walk your way through most of the Aethrys if you wanted too, outside of the Ring-Pass-Nots that exist between major sections of the Aethyrs.
ZAA Aerospace is a completely automated factory. You will not find any people here, outside of the Night Watchman who can help you on your journey through the huge factory complex; however he will not accompany you. This adventure you have to do on your own.
ZAA is about loneliness and learning to cope with it. In this place, you get to explore who you are without distractions. The goal in ZAA is to learn how to be an individual. Many people are part of the hive mind of humanity, and, as such, they are too reliant on those around them for their own identity.
In ZAA Aerospace, you will find nothing human to attach yourself into. The various automated machines go about their job without your intervention and even without noticing you. You are a spectator in this place. You can learn some valuable lessons about order and chaos from the factory floor, but otherwise you are in a world where you are the only living thing that exists.
The energy of disconnection from others is very strong in ZAA. You have to learn how to exist without the energy and influence from others, so that you can know who you are without them. You successfully complete ZAA when you can walk the factory from one end to the other without feeling regret, remorse or attachment to anyone else. You are able to be an individual and stand on your own if you have to.
Once you complete ZAA Aerospace, you can return here as much as you want for some deep relaxation and calm. While the machines are busy doing their thing, the rhythm of the automation is like a binaural beat putting you into a deep, sleep-like rejuvenating state of being. That is the gift you get for completing this Aethyr.
* additional source material: "Enochian Magick" by Gerald J. Schueler, "The Golden Dawn" by Israel Regardie