ProxyRequests off
<Proxy *>
    Order Allow,Deny
    Allow from all
</Proxy>

Redirect /znc https://server.domain/znc/
ProxyPass /znc/ http://localhost:port/
ProxyHTMLURLMap http://localhost:port/ /znc/
<Location /znc>
    ProxyPassReverse /
    SetOutputFilter proxy-html
    ProxyHTMLURLMap / /znc/
    RequestHeader unset Accept-Encoding
    RequestHeader set Authorization "Basic BASE64(ID:PASSWORD)"
</Location>