I can't check your program, as the archive is missing the following files needed for compilation:
Open-SaveFile.bi
OpenFile.bm
Replace.bm
open-folder.png.MEM
zip-folder.png.MEM
delete.png.MEM
Once again, there's no restriction on any file formats. However, very small files or those already compressed will probably fail even with a given ratio of 0%.
I see also, that you will run the LzwPacked data thru _DEFLATE$, which is probably of less use either. If the data is once packed with my LZW routine, then another _DEFLATE$ call (which is nothing else than a LZW derivate) will probably don't do much, although I guess the LZW implementation used by _DEFLATE$ is a better optimized algorithm than mine and could squeeze out another percent or two.