quiz_meta

$meta_query = array(
	'relation' => 'AND',
	array(
		'key'     => 'email',
		'value'   => '$email',
		'compare' => '=',
	),
	array(
		'key'     => 'quiz_id',
		'value'   => '$quiz_id',
		'compare' => '=',
	),
);