What utility are you using to zip the folder? Winzip? Does this utility have an option to log it's activity? If you are using a command line utility you can capture stdout and stderr to see what output it generates. Like this.
SomeZipProg.exe /parm1 /parm2 1>C:\temp\SomeZipProg.log 2>&1
You could also launch Task Manager and watch the details tab to monitor the performance of the zip program. I would expect that it's using up all of the pc's memory if its freezing. Kill the program before it uses up all of the system's memory.