The plot of this adventure fit very well into the story in my ongoing campaign, and I am always trying to avoid writing detailed dungeons and every little npc when someone else might have done the work already. So I gave it a try.

My gang loves moving their fancy little tokens all over battlemaps and this one had everything laid out nicely, so I made all the maps into roll20 maps. It took a lot of work converting the 4e monsters into 5e equivalents, though.

Also every single encounter was basically scripted to be a fight, which I did not like. Even given diplomatic/social options, it seemed very difficult for a PC party to come to any arrangement or alliance with the drow or any other npcs -- all the npcs' demeanors started at incredibly unhelpful, hostile, or they came off as so suspicious that the PCs with any brains would never trust them. I know that is how drow are supposed to be but it just seems completely implausible to have none of them cooperate with the party. Or in any event, it would be super boring. I think that is a common thing in 4e (I did not play 4e in its heyday) where everything is a fight or (in my opinion) an overly abstracted skill challenge.

An example was the death knight and his rakshasa that were camped outside the ziggurat. The encounter simply says that they attack anyone who comes near. This is after 10 or so encounters that basically have this same "AI". It seemed more interesting to do something different with this odd situation. I had the death knight be bored to tears waiting to be let in, and made it willing to parlay or at least exchange information with the party. I made him offer a duel one of the PCs one on one to let them either cut in line (if PC won) or agree to retrieve the magic sword inside for him (if the death knight wins). If they had found the sword, it would have been another conundrum for them to decide whether to hand over such a powerful weapon (especially since they had to walk back out that way).

But the maps were good and the drow city was laid out interestingly, and the story worked very well into the plot of my campaign. I also added a few encounters lifted from Out of the Abyss to flesh out the journey there.

I would recommend you make the final ziggurat larger than just the provided battlemap for the last fight. It could be a small/medium dungeon all on its own and thereby offer a final mini-adventure before the big fight.