Conditional URL rewrite for custom post type and taxonomy

We have a product register where we have products as a custom post type. Connected to this we have a custom taxonomy (product_cat). We have setup rewrites so that our permalink structure looks like this:

/product/tax-1/tax-2/our-product

For this, we used this in functions.php:

function product_rewrite_rules($rules) {
$newRules  = array();
$newRules['product/(.+)/(.+)/(.+)/?$'] = 'index.php?product=$matches[3]';
$newRules['product/(.+)/(.+)/?$'] = 'index.php?product_cat=$matches[2]';
$newRules['product/(.+)/?$']      = 'index.php?product_cat=$matches[1]';
return array_merge($newRules, $rules);
}
add_filter('rewrite_rules_array', 'product_rewrite_rules');

This has worked well, but for some taxonomies we need to add a third level, so permalink would look like this:

/product/tax-1/tax-2/tax-3/our-product

If we change our rewrite rules to:

function product_rewrite_rules($rules) {
$newRules  = array();
$newRules['product/(.+)/(.+)/(.+)/(.+)/?$'] = 'index.php?product=$matches[4]';
$newRules['product/(.+)/(.+)/(.+)/?$'] = 'index.php?product_cat=$matches[3]';
$newRules['product/(.+)/(.+)/?$'] = 'index.php?product_cat=$matches[2]';
$newRules['product/(.+)/?$']      = 'index.php?product_cat=$matches[1]';
return array_merge($newRules, $rules);
}
add_filter('rewrite_rules_array', 'product_rewrite_rules');

it works for three levels of taxonomies, but not two. We can’t figure out how to get this working. I we add a conditional like:

if ( is_tax(220) ) {
	$newRules['product/(.+)/(.+)/(.+)/(.+)/?$'] = 'index.php?product=$matches[4]';
	$newRules['product/(.+)/(.+)/(.+)/?$'] = 'index.php?product_cat=$matches[3]';
} else {
	$newRules['product/(.+)/(.+)/(.+)/?$'] = 'index.php?product=$matches[3]';
}

to try and run some rewrites for certain taxonomy pages and the old setup for others, it doesn’t seem to work. I can’t imagine that this is not possible to achieve, but it seems like we’re going about it the wrong way.