You plan to deploy an SAP landscape that will have virtual machines deployed to multiple...

Depending on the rules and restrictions you want to apply between the different virtual networks hosting VMs of different SAP systems, you should peer those virtual network

Note: Virtual network peering enables you to seamlessly connect two or more Virtual Networks in Azure. The virtual networks appear as one for connectivity purposes. The traffic between virtual machines in peered virtual networks uses the Microsoft backbone infrastructure. Like traffic between virtual machines in the same network, traffic is routed through Microsoft's private network only.

Azure supports the following types of peering:

Virtual network peering: Connect virtual networks within the same Azure region.

Global virtual network peering: Connecting virtual networks across Azure regions.