WordPress multisite – Rewrite multisite functions.php

Hi, hope my title was ok ??

I am converting a working site (that I made) to multisite.
Inside the functions.php I have a regexp for custom feed rewriting.

I think it must collide with the htaccess code that the multisite told me to replace the contents inside the htaccess file with.

My current htaccess:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

Then I have this rewrite inside the functions.php:

function custom_feed_rewrite($wp_rewrite) {
	$feed_rules = array(
		'feed/(.+)' => 'index.php?feed=' . $wp_rewrite->preg_index(1),
		'(.+).xml' => 'index.php?feed='. $wp_rewrite->preg_index(1)
	);
	$wp_rewrite->rules = $feed_rules + $wp_rewrite->rules;
}
add_filter('generate_rewrite_rules', 'custom_feed_rewrite');