Given a "nacked" Zend application - is it possible to use the Drupal based layout and navigation?

What is the best way to integrate a Zend application into Drupal 6 / Drupal 7?

For Example:

User X visits my Drupal page.

He wants to use the Zend-Application called "Feedback".

This "Feedback" application should be able to use the layout of the Drupal page.

Everything but the outer layout would be written in PHP using Zend.

php zend-framework drupal integration
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