You can use JOIN queries in your code to make it in one call. From what I understand, you want to build this query
SELECT p.*, c.*, s.date_of_sale FROM sales AS s
INNER JOIN products AS p ON p.product_id = s.product_id
INNER JOIN customers AS c ON c.customer_id = s.customer_id
WHERE p.product_id = '1';
To achieve this, you can refer to Complex SQL query into Zend to see how I translate it to a Zend_Db Query or just use something like
$select = $this->select()->setIntegrityCheck(false);
$select->from(array('s'=>'sales'), array('date_of_sale'));
$select->join(array('p'=>'products'), 'p.product_id = s.product_id', '*');
$select->join(array('c'=>'customers'), 'c.customer_id = s.customer_id', '*');
$select->where('p.product_id = '.$productId);
Obviously, it would be better to quoteInto the where clause but I'm just too lazy.
Hope this helps !