Nested for loop

With a combination of libarchive's bsdtar and GNU tar, you can list the contents of those nested archives without having to extract them on disk:

for f in *.zip; do
  bsdtar -cf - --include='*.zip' "@$f" | tar -xf - --to-command='bsdtar tvf -'
done

GNU tar can pipe members of archives to commands upon extraction with --to-command but only supports tar archive formats.

bsdtar supports all sorts of archive formats beside tar ones (including zip ones), doesn't have the equivalent of GNU tar's --to-command (AFAIK), but can convert archive formats on the fly.

You can't do it without actually unzipping the top files in a sub-folder.

Something like this:

set -e
for f in *.zip
do
  n=`basename -- "${f}" .zip`
  mkdir -- "${n}"
  cd -- "${n}"
  unzip ../"${f}"
  for p in *.zip
  do
    unzip -l -- "${p}"
  done
  cd ..
  rm -rf -- "${n}"
done

You should probably verify whether ${n} already exists and if so generate an error. You could also use a temporary filename for the sub-directory:

dir=`mktemp -d zip-files.XXXXXX`

Then do cd "${dir}" and rm -rf "${dir}" once done.

Updates:

The set -e is used to make sure that if something goes wrong then the script stops. Especially, if the mkdir -- "${m}" fails, the cd -- "${m}" will fail too and thus the cd .. would get you at the wrong directory level and that's where the rm -rf -- "${n}" becomes dangerous.

Another way to make the cd .. statement safer is to memorize that directory before the for loop and use that path like so:

topdir=`pwd`
for ...
do
  ...
  cd "$topdir"   # instead of `cd ..`
  ...
done

That way the rm -rf -- "${n}" will only operate in $topdir.

The use of the temporary directory will also make things a lot safer since that way whatever the filenames in the top zip file, the directory creation/removal will work as expected.

If GNU Parallel is installed:

extract_list() {
  mkdir "$1"
  cd "$1"
  unzip ../"$1".zip
  parallel unzip -l ::: *.zip
  cd ..
  rm -rf "$1"
}
export -f extract_list

parallel extract_list {.} ::: *.zip