# BEGIN WordPress

RewriteEngine On

RewriteBase /

RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin

RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]

RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^ - [L]

RewriteRule ^(wp-(content|admin|includes).*) $1 [L]

RewriteRule ^(.*\.php)$ $1 [L]

RewriteRule . index.php [L]

# END WordPress

and we will replace it with:

# BEGIN WordPress

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]

# END WordPress