title: Relationship between two taxonomies
body: <p>for a project, I've a CPT products with two taxonomies : category and brand.</p>
  
  <p>I would like to build a navigation from a category to a product under a brand.</p>
  
  <ul>
  <li>page 1 : list the categories terms</li>
  <li>page 2 : list the brand term having the selected category term</li>
  <li>page 3 : list the products under the brand and the category</li>
  <li>page 4 : display the product</li>
  </ul>
  
  <p>Obviously, page 1 and 4 are easy to do but i can't figure out how to retrieve the terms in the page 2 and the products in the page 3.</p>
  
  <p>I'm sure there is a way to do that. Any idea ?</p>
  
  <p>Thanks.</p>
  
  <p>Cyril</p>