Question: /controller/action

but what if we have

/controller/action/subaction

How do you add this "subaction" to controller?

Answer: 
There are no sub-actions in an MVC design.

What you can do is set "subaction" as a parameter or argument to the action. If you don't want to use the default `param/value` pairing, you would need to set up a custom route to recognise a single value.

To choose a different view, you use the `ViewRenderer` action helper. See [ZEND, rendering different view with data](https://stackoverflow.com/questions/4856928/zend-rendering-different-view-with-data/4857115#4857115)
you can create Facades somewhere else, then write mod\_rewrite to redirect all ^/controller/.\* URLs to /controller/ and redirect all requests in init() method to correspondent method in Facade

you can also try to create something like YourController that extends Zend\_Controller\_Action, and modify all controllers to extend that controller