PPTP Passthrough Centos 7/Firewalld router to Windows Server

I have a Centos 7 server running firewalld to allow public services to access internal services on a separate VLAN (dual NICs). I imported a Windows VM but I do not know what rules I need to put in place to allow GRE through firewalld, other than opening 1723. All the questions and guides I find online never to setting PPTP on the Centos 7 box itself, rather than passing it through to a routed IP (in this case the windows server).

On my rhel7 servers which allow access to a PPTP VPN I set the following in addition to opening the port:

sudo firewall-cmd --permanent --zone=public --direct --add-rule ipv4 filter INPUT 0 -p gre -j ACCEPT
sudo firewall-cmd --permanent --zone=public --direct --add-rule ipv6 filter INPUT 0 -p gre -j ACCEPT
sudo firewall-cmd --permanent --zone=public --add-masquerade
sudo firewall-cmd --reload