*** The 'Z' command on a directory name compresses all of its files.
It produces a compressed '.tar.gz' archive with all the files in the
directory and all of its subdirectories. For symmetry, 'Z' on a
-'.tar.gz' or a '.tgz' archive extracts all the archived files into a
+'.tar.gz' or a '.tgz' archive extracts all the archived files into
+the current directory; thus, typing 'Z' on a '.tar.gz' archive created
+by a previous 'Z' command will extract the archived files into a
directory whose name is the archive name sans the '.tar.gz' or '.tgz'
extension. (This change was actually made in Emacs 26.1, but was not
called out in its NEWS.)