It's pushing up daisies is what it is. An old library module that existed about five years ago--you can find some information in the documentation for older GHC releases. I'm guessing that the code you're trying to compile is of a similar age.
Assuming there isn't an updated version of zinc somewhere, your choices are roughly:
- Use an antique version of GHC to build it.
- Update the code yourself to import whatever modules the contents of
IOExts
ended up in.
- Create a mock-IOExts module that reexports the necessary stuff.
Assuming there aren't other problems, the third is probably easiest as a quick hack. There's a fair chance you'll run into more compatibility issues than just this one, though, so grabbing a copy of GHC 6.4 might be the simplest thing overall, particularly if you're not sufficiently comfortable mucking about with the source code.