This has been one of my favourite modules of season 7 so far. It is not recommended as an emergency pick up and run without prep.
There are a few consistent criticisms that I read in reviews here when prepping and I agree with.
1- continuity with Wadumu in description (colour), and character (part 3) - his betrayal really doesn't make sense.
2-It is a long adventure and better suited to 4 hours.
I ran for a small party (Very Weak) and they had difficulties with the first part due to numbers. The waves of zombies really took their toll on resources, but they really seemed to enjoy it. They also wasted a lot of time trying to explore the ruins of the buildings on the outskirts. I would recommend to anyone recreating the maps to zoom in and just include the clearing as the buildings are a distraction.
The clues to the door lock is on the flipside of the page describing all the defenses, so the whole section needs to be read in advance to prep it. . I printed the clues on a handout which I distributed as each riddle was read. I think was helpful for the players. It takes a little extra prep to get everything sorted (e.g. the description when doorway is opening not included in original description), but is worth it.
I asked players to prepare some character background info to prepare for part 2 which freaked them out to everyone's enjoyment (good place for Xanathar's tables). If your room allows it, I'd recomend walking around the table, to make it seem like the voices are coming from all over the cavern.
I think the adjustments for a very strong party would be tough, but more entertaining. The legendary actions for the BBEG were quite impressive,but the very weak adjustments were very easy (but time consuming). for a resource drained weak party to defeat.
One character almost died staying behind to kill zombies in part 3.
Guild Adept adventure Hunter fits very well before or after this adventure
[4 of 5 Stars!]