Virtual Subdomains with .htaccess , and rewriting links inside it

I have successfully created virtual sub-domains using .htaccess
Now I need to make second url rewriting of these subdomains, for example:
subdomain.domain.com/index.html will show the content of subdomain.domain.com/index.php but still keeping subdomain.domain.com/index.html in the adress bar.
in public_html I use inside .htaccess:

RewriteEngine on
DirectorySlash off
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.([^\.]*)\.domain\.com$ [NC]
RewriteRule (.*) http://%1.domain.com/$1 [R=301,L]
RewriteCond %{HTTP_HOST} ^www.domain.com$ [NC]
RewriteRule ^(.*)$ http://domain.com/$1 [L,R=301]
RewriteCond %{HTTP_HOST} ^(.*)\.domain\.com$ [NC]
RewriteRule ^(.*?)/?$ http://domain.com/users/%1/$1/ [P]

Code (markup):

but I can't find a working solution to rewrite subdomain.domain.com/index.html >> subdomain.domain.com/index.php
I tried creating .htaccess inside /users/subdomain/ :

RewriteRule ^index\.html$ index.php [L]

Code (markup):

But it just does nothing !!