Hello:
Try these steps:

1) grab and install http://maemo.org/downloads/product/OS2008/unzip/
2) place zip file in a temp dir (i.e. /media/mmc1/zipjunk)
3) open xterm window and change to temp dir (i.e. cd /media/mmc1/zipjunk)
4) type unzip *.zip (if you want you can also type 2 or 3 characters of the file name and tap the tab key and it should auto-magicly complete the horribly long file name that the zip archiver chose to use)
5) use file manager to move unzipped files to where you want them

This is a quick and dirty way to accomplish unzipping for more ideas try typing unzip at the prompt in xterm and it will provide you with other options for dealing with those pesky files

Have fun
ben