How to delete an old Firefox account?

I recently created a new Firefox account using my new gmail address. I still have an old Firefox account associated with an old gmail address that was compromised; I would like to delete the old Firefox account. When I try to sign in to the old Firefox account, I'm told I'll have to sign in using my "primary" account--presumably the new account. When I sign in to the new account, I only see an option to delete the new account, which I don't want to do, as I have Firefox Relay and passwords connected to it. How do I delete (only) the old Firefox account? Thanks.