[PeterT]

Not sure how / where you are getting these comics but trying to view this under Linux I get

Spoiler:

unzip -t /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz 
Archive:  /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz or
        /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz.zip, and cannot find /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz.ZIP, period.

Additionally

Spoiler:

file /mnt/chromeos/MyFiles/Downloads/efpnw8.cbz 
/mnt/chromeos/MyFiles/Downloads/efpnw8.cbz: 7-zip archive data, version 0.3

cbz / epub are both zip files and should be openable by any zip tool.

cbr is a rar and should be openable by any rar tool.