Experimente assim:
RewriteCond %{HTTPS} on
RewriteCond %{HTTP_HOST} **Insert current condition here ***
RewriteRule ^(.*)$ https://%{SERVER_NAME}\.xyz.com%{REQUEST_URI} [R]
RewriteCond %{HTTPS} off
RewriteCond %{HTTP_HOST} **Insert current condition here, but for https***
RewriteRule ^(.*)$ https://%{SERVER_NAME}\.xyz.com%{REQUEST_URI} [R]