This begins you on the quest of The Lost Expedition, whose goal is to locate the four missing researchers- Stromm, Erj, Krag, and Staubs. This, naturally, can only be done by fully exploring Nchuand-Zel and, hey look, you came here prepared to do that anyway. How fortunate!
Bash or tear open the web to access the door that admits you to Nchuand-Zel itself.
Your initial look into Nchuand-Zel is from the central area of the city, a kind of ‘hub’ for the entire ruin. Stepping through a narrow corridor, you come across a large, rough cavern with deep water on the floor. Thankfully, you aren’t on the floor- you’re several ‘layers’ of Dwemer stonework up from the floor. For the sake of simplicity, although you can take some risky leaps and make your way quickly down, I am going to assume you aren’t interested in potentially neck-breaking falls and would rather explore the city without a chance of plummeting to your doom, thank you very much.
You should start by taking care of the three Falmer, one ordinary, a Shadowmaster, and two Gloomlurkers, one of whom is a spell-and-sword wielder and the other of whom prefers archery. The ordinary Falmer is the one nearest to you, with the Gloomlurkers (naturally) lurking about in the gloom on the farther parts of the top layer of stone bridges. The Shadowmaster is at an in-between distance, lingering on the edge of a ledge coming off the side of the first tower- if sniped, it will likely keel over the edge of the stonework and plummet into the water below. Sneaking and archery or spellwork can make things relatively safe here, while charging in, weapon swinging can get the job done equally well with more risk and less time spent. Snipers may also wish to take this opportunity to take out a couple of Falmer that can be seen on lower levels- feel free to do this, as they have virtually no chance to ‘see’ you at such distances and likely can’t reach you outside of archery anyways.
Since your first task is to find Stromm’s journal, you’re going to want to stay on the top layer of the stonework, crossing to the far tower and then using the visible door to the left to enter the Nchuand-Zel Quarters Upper Level. You will begin in a smallish hallway, with a small nook in the left side. Check the nook for some smeltable Dwemer metal, and then proceed around the corner to the right. You will quickly get a view of a Falmer who is waiting at the top of a stairway, which leads down to the lower level of the Nchuand-Zel Quarters- but you don’t want to go down yet.