After installation, it should show up in your start menu or application launcher due to the included desktop file. The CLI is called zeditor instead of zed or zed-editor because we also have a database called zed in nixpkgs and because zeditor is one of the alternative CLI names suggested by upstream (if zed can’t be used). I personally (as one of the package maintainers of zed-editor) don’t like that we renamed the CLI and would prefer going back to just zed.
Edit: as a funny observation, another program called zed (spicedb-zed) exists in nixpkgs, and that one did not go out of its way to avoid the binary name collision.
Edit 2: spicedb-zed is actually the oldest zed in nixpkgs (added 2022-08-06), while the package called zed has been added just a week after (2022-08-11). I’m not convinced it’s likely enough any of these three will be installed at the same time to keep on confusing zed-editor users with the CLI name differing from upstream.