thenorthman,
Welcome to the Crusade. The Trolls produced a few products for Castle Zagyg.
1. Gary Gygax's Castle Zagyg: Yggsburgh
2. Gary Gygax's Castle Zagyg: Upper Works
The first is a hardback book that detailed a free city similar to the Free City of Greyhawk and all the surroundings, plot hooks, and adventures.
The second was a box set, which had multiple modules within. This was the actual Castle Zagyg and the upper areas and 1st level cellars.
Other things done for CZ was a module called the Dark Chateau which was kind of the summer residence, or the home before and during the building of Castle Zagyg. In addition, there were a series of modules released that described the various areas of Yggsburgh in detail, with NPCs, plot hooks, adventure areas for specific sections of the city. I don't know off hand the names of each of them.
That's all they made as far as I know. And once Gary passed, his spouse made the decision to move the license from the Trolls, so it's all out of print and not sold in PDF either.
If your looking for something similar, consider this. Joesph Bloch of the Greyhawk Grognard blog
http://greyhawkgrognard.blogspot.com/20 ... -sale.html
went ahead and made sort of tribute/fan dungeon crawl based off the ideas that were out there on the plan of Greyhawk/Zagyg called The Castle of the Mad Arch Mage. Initially a free offering, he's now expanded it to full fledged dungeon crawl (not that the free one wasn't, he took it up to 11 with a map book, illustration book, and included additional levels). And re-imagined the Upper Works. It's made for his Adventures Dark & Deep (AD&D) by his company BRW Games, which is compatible with any OSR rules including C&C. It's offered in PDF and print on demand softcover or hardcover. (Sale going on now thru the 22nd of June for 30% off).
Anyone else have any thing to add?