Make accesible subdomain.domain1.com on one VPS from domain1.com from another VPS with both VPSes on Hyper-V beheind Mikrotik, pfSense and Virtualizor

subdomain.domain1.com is accesible from Internet but not accesible from domain1.com/nextcloud

Network:

Mirotik -> Hyper-V:
--> VPS 1.1. pfSense --> VPS 1.2 CentOS Web Panel with domain1.com/nextcloud (through Cloudflare) adn
--> VPS 2.1. Ubuntu20 Virtualizor -> VPS 2.2. Ubuntu20 subdomain.domain1.com