Using specific dns server for specific domains

Have you tried this PowerShell command? Seems a lot easier.

Add-DnsClientNrptRule -Namespace "pqr.com" -NameServers "10.0.0.1"

Reference: https://docs.microsoft.com/en-us/powershell/module/dnsclient/add-dnsclientnrptrule?view=win10-ps

You can do this with DNS zone delegation.

First, set up another DNS server (on your own machine is fine) that uses unblock-us.com DNS as a forwarder. You could use something like Simple DNS, MaraDNS, or a local virtual machine running Linux or Windows Server.

Second, add a delegate zone for your company's network that points to your company's DNS servers.

Third, configure your network card to use your new DNS server as the primary name server.