znew —
convert compressed files to gzipped files
The znew utility uncompresses files compressed by
  compress(1) and recompresses
  them with gzip(1).
The options are as follows:
  - -f
- Overwrite existing ‘.gz’ files. Unless this option is
      specified, znewrefuses to overwrite existing
      files.
- -t
- Test integrity of the gzipped file before deleting the original file. If
      the integrity check fails, the original ‘.Z’ file is not
      removed.
- -v
- Print a report specifying the achieved compression ratios.
- -9
- Use the -9 mode of gzip(1),
      achieving better compression at the cost of slower execution.
- -K
- Keep the original ‘.Z’ file if it uses less disk blocks than
      the gzipped one. A disk block is 1024 bytes.
Theznew utility tries to maintain the file mode of the
  original file. If the original file is not writable, it is not able to do that
  and znew will print a warning.