Making file permissions match

I'm working with some Windows programmers that don't believe in file permissions They keep sending me zip files of their source tree. I have my copy of the tree in git on Linux with all of the correct file permissions.

So I unzip the archive they send me and to see what they changed. I unzip it on top of my git tree. But now all of the file permissions don't match. The code deltas are there but there is also all of this noise from the file permissions.

Is there an easy way to deal with this? I want to keep the code deltas and ignore the permission changes. Since there are about 100K files this is too much to do manually.