Alter zip file without unzipping

I have some zip files. Every file has a "folder/xml file" inside it. Is there any way to change these zip files directly without unzipping them. I want to convert these zip files to "/xml file" (want to move the xml file/s one root up by removing the folder inside it.)

Ex:
-bash-3.00$ for file in *.zip; do echo $file ; zipinfo -1 $file ; done
100_xxxx.zip
20081106/Test1.xml

I wan to change this zip file so that it will look like this :
-bash-3.00$ for file in *.zip; do echo $file ; zipinfo -1 $file ; done
100_xxxx.zip
Test1.xml

Can anyone help. Any help or clue is appreciated.

From reading the man page, I guess you could unzip the xml file from the zip file, then use the -d option to remove it from the zip file, then use the -g option to update the xml file's new position into the archive. I'd make a backup of your files first, if you know what I mean...

Are the files too large to unzip, is there something about the timestamps you want to preserve, or what?