I don't want to use the non-Zip format because I want people to be able to decrompress the files with other programs if they wish.
I suppose I could load InfoZIP's dll, but I'd prefer if the EXE would be self contained.
Is there an unzip function available?
No, there is no "unzip" function available. The reason for that is that creating a simple zip file is much easier than unzipping a zip file. madZip is built in such a way that is just does whatever is necessary to create a simple zip file. madZip doesn't even support all the funny compression formats the ZIP format can handle. So if you tried unzipping a zip archive with madZip, there'd be some zip files that simply wouldn't unzip at all.