Your company has a project in Google Cloud with three Virtual Private Clouds (VPCs) to maintain network isolation. Each VPC contains one Compute Engine instance, and the subnets across these VPCs do not overlap. For security and organizational reasons, the subnets must remain separated. However, there is a requirement for Instance #1 to communicate directly with both Instance #2 and Instance #3 using internal IP addresses. How should you accomplish this while ensuring the VPCs remain isolated?