03-10-2013 08:56 PM
I just tried to zip a couple of pdf files, several pictures and all the files size's change. It is possible that the file you are trying to zip might already be compressed. I am sure that the built in zip feature is not setup for super high compression. Where you notice a big diffrence is when you select a lot of files and zip it..
Bellow is a picture that was zipped.. It did compress the file size. But the file was already compressed when I downsized the image for the z10. Try other files on your device to see if they all have the same issue.