Category and post tag archives do not include posts from custom post type

By default, WordPress will only include the post post type within the post_tag and category taxonomy archives.

Use this snippet to add newz posts to the post_tag and category taxonomy archives:

add_filter( 'pre_get_posts', 'wpse_newz_taxonomy_archives' );
function wpse_newz_taxonomy_archives( $query ) {
  if ( $query->is_main_query() && ( is_category() || is_tag() ) ) {
        $query->set( 'post_type', array( 'post', 'newz' ) );
  }
}