Prevent Editors from Editing/Deleting Admin Accounts

There is a function WordPress uses called get_editable_roles, which is (I think) used to determine which roles a particular user can edit. The source for this function looks like this:

function get_editable_roles() {
    global $wp_roles;

    $all_roles = $wp_roles->roles;
    $editable_roles = apply_filters('editable_roles', $all_roles);

    return $editable_roles;
}

So, it looks like you may be able hook into the *editable_roles* filter to get what you’re looking for. Something like this:

function wpse_80220_filter( $roles ) {
    $current_user = wp_get_current_user();

    if ( in_array( 'editor', $current_user->roles ) ) {
        unset( $roles['administrator'] );
    }

    return $roles;
}
add_filter( 'editable_roles', 'wpse_80220_filter' );

I haven’t tested any of the above code, but play with it and let me know if it does the trick!