Root site .htaccess interferes with WordPress - regex

Question

I admit, my .htaccess/regex is the weakest part of my game in development. It's a problem, especially today.
I've got a client's root site in ASP, the access on public_html is applied as follows:
RewriteEngine on
RewriteRule ^$ index.php [L]
RewriteCond $1 !^(index\.php|robots\.txt|favicon\.ico|xmlpdf\.cfm|public|dynamic|googlead5e4138365a1f11.html|sitemap.xml)
RewriteRule ^(.*)$ index.php/$1 [L]
Options -Indexes
They want to install WordPress in /public_html/inventory. Obviously, the recursive nature of .htaccess is causing huge conflicts. Problem is, I'm not entirely sure how to resolve a conflict of this nature. Not that anyone here needs the review, but the default WP .htaccess is:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
I'm hoping someone can tell me how to relinquish the root folder's icy grip on the WordPress sub-folder.
Thanks bunches.

Answer 1

This should be root .htaccess:
Options -Indexes
RewriteEngine on
# skip WP dir
RewriteRule ^inventory(/|$) - [L,NC]
RewriteRule ^$ index.php [L]
RewriteCond $1 !^(index\.php|robots\.txt|favicon\.ico|xmlpdf\.cfm|public|dynamic|googlead5e4138365a1f11.html|sitemap.xml)
RewriteRule ^(.*)$ index.php/$1 [L]
This should be WP /inventory/.htaccess:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /inventory/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php [L]
</IfModule>