Something I still don't get (IFS directory authorities, zipping a tree, and unzipping it elsewhere)

Here's the situation:

I create a directory (for argument's sake, call it "foo"), with a bunch of subdirectories in it, most of which themselves have a bunch of subdirectories, by calling mkdir() from an RPG program. At every level of that directory tree I've created, I made everything RWX owner, RWX group, RWX public.

In WRKLNK, option 9, the authorities for "foo" and its children and grandchildren show as:
User Authority Exist Mgt Alter Ref*PUBLIC *RWX X X X X
ME *RWX X X X X
and
User Authority Objopr Read Add Update Delete Execute

*PUBLIC *RWX X X X X X X
ME *RWX X X X X X X

In QP2TERM, an "ls -l" shows the modes for "foo" and its children and grandchildren as "drwxrwsrwx."


I then zip that directory, using the InfoZip version of ZIP, via PASE.

If I then unzip it into my home directory, on either my Mac, or on a Google Compute Linux instance, though, while all the children and grandchildren remain fully accessible to all ("drwxrwxrwx"), "foo" itself loses its public and group write authorities, i.e., "drwxr-xr-x."

And on my Mac, even if I stick the zip file into a directory that's "drwxrwxrwx," and unzip it there, it still ends up "drwxr-xr-x."

Can somebody explain what's going on here?

--
JHHL