Use WP_query to match post types based on custom field values

In the WP Docs you can find the answer.

I have not tested this snippet, but it should become something like this:

$args = array(
    'post_type'  => 'product',
    'meta_query' => array(
        'relation' => 'AND',
        array(
                'key' => 'product-ean',
                'value' => 123,
                'compare' => '=',
        ),
        array(
                'key' => 'item-ean',
                'value' => 123,
                'compare' => '=',
        ),
    ),
);
$query = new WP_Query( $args );