So, you have a set of files, that you have made an archive using "tar", which will create one output file. Then, you used "gzip" to compress that one ".tar" file into a ".zip".
If that's the case, then the process of getting a listing of all the files in the ".tar" file, requires that the ".tar" file must be fully unzipped from the ".zip" file, before the contents of the ".tar" file can be listed.
This will always take more time than getting a listing of the files that are stored "directly" in a ".zip" file. If the file is large, this time can be considerable.
If you want to reduce the time required to list the files in a compressed archive file, then:
unzip (uncompress) the ".tar" file from the ".zip" file, and expand the resulting ".tar" file into the underlying fileset
create a ".zip" file directly from the set of files.
This way, the files in the archive file can be listed without uncompressing the archive.