Most, if not all the ZT Design files need updating one way or another. Many were exe loading and put the files in the Updates folder instead of the dlupdate folder for those with MM, and CC. Also they added files to the main folder in some cases, which you would not know to delete when you removed the file. Most contain an LCID error which will cause some people's games to crash - this is dependant on the language setting people may have for their game.
ZKL had permission to host some, but not all, files while ZT Design was around.
Zoo Tycoon Community Downloads Directory (ZTCDD) now has permission to update and host all the files. When they are fixed and uploaded is dependant on when I get time to do them as currently I have a large volume of new files to get ready for release and there are a huge amount of files out there that need updating for one reason or another.
Some files contained ids that conflicted with creations of other sites. The Mystery Tree conflicts with a ZA file, is one that comes to mind.
One thing I will be doing is creating a combined dll for ZT Designs, as many used patch dlls which are known to cause sporadic problems.
Many of the buildings were done at a time when not much was known about what ZT did with food, drinks and benches etc. If you look at the listings at ZTCDD, you will find many contain warnings about early created buildings hosted at ZKL which need fixing including some of the ZT Design ones. For example, if you look at the KFC Theme Pack there, you will see 3 warnings in the same pack, all of which should be fixed.