re-zipped docx files don't open in Word

I've had success unzipping and examining the interior of a .docx file, but I can't seem to get the re-zipping to work properly. I've tried no compression (command line: zip -0r ...), the archive utility, and a 7zip plugin but none of that works. All of the .docx files I create won't open in the original programs, even when I don't change a single file. Any tips?

It is important that the files that make up the docx are not within another folder, i.e. [Content_Types].xml must be in the root of the resulting zipped file. A similar question has been asked on StackOverflow.

When you open (or extract to the current directory) the zip file, you should have something similar to the following:

./docProps/
./word/
./_rels/
./customXml/
./[Content_Types].xml

If you have those files within another directory inside the zip or docx file, it won't work. Note that I don't get the customXml folder on an empty Word document, but the report I originally tested with did have it. You may have some more (or less) directories.

The command to rezip these, issued from the "current directory", is:

zip -r preso.pptx *