how to rename a module in the url with mod_rewrite - .htaccess

Question

I'm using MVC with /<module>/<controller>/<action>/ have a module at example.com/module/whatever, and I need to 'rename' it to example.com/module-a/whatever. The whole application is already written, so I can't go through and change it everywhere in my code, so I'm hoping to do it with mod_rewrite. I've tried the following
RewriteCond %{THE_REQUEST} ^GET\ /module/
RewriteRule ^module/(.*) /module-a/$1 [L,R=301]
which did what I wanted as far as redirecting all urls like example.com/module/whatever to example.com/module-a/whatever, but now I need all requests at 'module-a' to be internally rewritten as 'module'. It also needs to work for the module root (i.e. example.com/module with no trailing slash). Is this possible? I added
RewriteRule ^module-a/(.*)$ module/$1
directly beneath the above condition and rule, but when the page is accessed, it still says the module 'module-a' is not found.
Edit:
I have a few more rules below those, I wouldn't think they would affect this, but here they are anyway:
RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
RewriteRule ^.*$ index.php [NC,L]
Solution
I ended up using
RewriteCond %{THE_REQUEST} ^GET\ /module/
RewriteRule ^module$ /module-a [L,R=301]
RewriteRule ^module/(.*) /module-a/$1 [L,R=301]
to redirect all links from module to module-a. I had to do it with 2 rules because I don't know regex well enough to combine them, handling the special case of the url example.com/module.
To rewrite internally, the original rule I had would normally work, but Zend seems to do some stuff that overrides that, so I had to handle it with routes. See rename a zend module with routes

Answer 1

If I understand correctly then you've gone about this from the wrong direction. I am also not clear on the purpose of your RewriteCond
You want all module-a/* requests to be processed internally as module/*, so all you need is a simple rewrite::
RewriteRule ^module-a/?(.*) /module/$1 [L]
I suspect the problem you are having is the internal links on the site all reference /module/ rather than /module-a/, but putting a 301 there will cause no end of problems (not least with search engines), and with the subsequent rewrite you may fall into circular references. You are much better off changing the link code in your app (if you have a link abstraction class), or at worst using output buffering to swap all links out before rendering the page.
Note: The second rule below the above is not being processed if the first matched, as [L] causes mod_rewrite to cease processing if that rule is matched.