Hmm probably use the Shell command to run winzip and create the zip file, then in the loop use another shell command to add the files you want to the zip.
Look in the help file chap! You're on the right track with having the path in a string. You'll also need to know the command line syntax for your compression program (there's one that comes with DOS called compact - type compact /? |more at the command line)
I believe that you need to know what zip tool your pc is using because if you have say WinZip installed then you can't use the windows default zip tool.
I have attached a demo of using a dll to zip files/folders in one command line. I am oing to post it in the samples forum later. here is a sneak preview. It's an old one but it works.