Compress file as .tar.gz instead of .zip
You can try to write a unix shell script where your commands are to tar the selected files then run gzip on it.

Then you can make this a service and save it at ~/Library/Services. Then enable it via system preferences > Keyboard > shortcuts > Services. 


Creating System-Wide Keyboard Shortcut To Launch Applications
How do I run my automator service without opening automator?


Then you can select a file and right-click on the selected file. At the bottom of the right click menu,  a section for Services appears which has your services. Select your new service and that should do the job.

Alternatively, it can be found in Finder menu > Services.