Thanks for the useful post. It worked for me although my dependency imports caused linting errors as ESLint expected to see my module listed in the package.json file.
Rather than figure out how to configure the import resolver I opted for installing the submodule as a local file path using
npm i -D ./modules/zc-core
As the path to the module is specified in
.gitmodules this should always point the bundler to the correct location and avoids having to use
rn-cli.config.js at all.