How to have a hierarchy of custom post types and use two of them in the permalink?

You can do this with custom hierarchical taxonomy and use it for your custom post type.

Register the Taxonomy area for the post type content using the init action hook:

function wporg_register_taxonomy_area() {
   $labels = array(
     'name'              => _x( 'Areas', 'taxonomy general name' ),
     'singular_name'     => _x( 'Area', 'taxonomy singular name' ),
     'search_items'      => __( 'Search Areas' ),
     'all_items'         => __( 'All Areas' ),
     'parent_item'       => __( 'Parent Area' ),
     'parent_item_colon' => __( 'Parent Area:' ),
     'edit_item'         => __( 'Edit Area' ),
     'update_item'       => __( 'Update Area' ),
     'add_new_item'      => __( 'Add New Area' ),
     'new_item_name'     => __( 'New Area Name' ),
     'menu_name'         => __( 'Area' ),
   );
   $args   = array(
     'hierarchical'      => true, // make it hierarchical (like categories)
     'labels'            => $labels,
     'show_ui'           => true,
     'show_admin_column' => true,
     'query_var'         => true,
     'rewrite'           => [ 'slug' => 'area' ],
   );
   register_taxonomy( 'area', [ 'content' ], $args );
}
add_action( 'init', 'wporg_register_taxonomy_area' );

Register custom post type content using the init action hook:

function my_custom_content_item() {
    $labels = array(
        'name'               => _x( 'Content', 'post type general name' ),
        'singular_name'      => _x( 'Content', 'post type singular name' ),
        'menu_name'          => 'Content'
    );
    $args = array(
        'labels'        => $labels,
        'public'        => true,
        'has_archive'   => true,
        'taxonomies'    => array( 'area' ),
        'show_in_rest'  => true,
    );
    register_post_type( 'content', $args );

} 
add_action( 'init', 'my_custom_content_item' );

Adds the registered taxonomy area to object type content.

function attach_area_to_content() {
    register_taxonomy_for_object_type( 'area', 'content' );
}
add_action('init','attach_area_to_content');