A network engineer is designing hybrid connectivity using AWS Direct Connect and AWS Transit Gateway. The transit gateway is connected to a Direct Connect gateway and 19 VPCs across multiple AWS accounts. Two additional VPCs are being attached to the transit gateway, with IP address assignments of 10.0.32.0/21 for the first VPC and 10.0.40.0/21 for the second VPC. The prefix list has only one CIDR block remaining before reaching its maximum entry limit.

What steps should the network engineer take to advertise the routes from AWS to on-premises while adhering to these constraints?