Unreal Online Learning: I can't fully unzip "Creating PBR Materials"

Hi all,

This concerns the “Creating PBR Materials” course from the Unreal Online Learning Portal by Matt Doyle.
I haven’t had any trouble extracting other courses.
There seems to be 2 files in the main zip file but one of them is another zip file.
I can’t unzip the second zip file because I keep getting something about inserting another disk which I think is the other file in the main zip.

Thanks for any help.