On Windows I use:
7za a "\bla\example.mysuffix" "\bla\source*"
This creates the ZIP file, but the Packed column shows 0 for all files (e.g. in WinRAR). Creating the ZIP with Windows File Explorer or WinRAR it shows the packed file size, which I think is as expected.
This seems to be the latest stable version of 7za (126.96.36.199, x64), from: