product_tag_cat

$tax_query = array(
	'relation' => 'OR',
	array(
		'relation' => 'OR',
		array(
			'taxonomy'         => 'product_cat',
			'terms'            => array( '1', '3', '4' ),
			'field'            => 'term_id',
			'operator'         => 'IN',
			'include_children' => true,
		),
	),
	array(
		'taxonomy'         => 'product_tag',
		'terms'            => array( '4', '1', '7', '8' ),
		'field'            => 'term_id',
		'operator'         => 'IN',
		'include_children' => true,
	),
);