Ok, so if you want to provide this view with the two buttons instead of Auth0 doing it with its login page, then you would trigger the auth0.loginWithRedirect request when the user clicks one of the two buttons and put the connection parameter, as shown above, dynamically based on which button the user clicked.
Relevant API docs for passing the connection parameter with the auth0-spa-js:
https://auth0.github.io/auth0-spa-js/interfaces/popuploginoptions.html#connection