How to gzip multiple files into one gz file?
if you have zip,
zip myzip.zip cvd*.txt
Don't need to tar them first.
You want to tar your files together and gzip the resulting tar file.
tar cvzf cvd.tar.gz cvd*.txt
To untar the gzip'd tar file you would do:
tar xvzf cvd.tar.gz -C /path/to/parent/dir
This would extract your files under the /path/to/parent/dir directory