Dynamic Block not showing
Your code works fine for me so I'd check the following:


Make sure the module's installed and enabled.
Make sure the module is definitely named zillow (the module file should be called zillow.module, info file zillow.info, etc).
Make sure you've cleared Drupal's caches.


I realise these might be obvious solutions but as I say the code works for me so I can only guess your hooks are not being called for one of the reasons above.