You need to assign a proximity placement group for VMSS1. Which proximity placement group(s) should you use?

Proximity placement groups are used to co-locate Azure resources, such as virtual machines, within the same data center to achieve the lowest possible latency. For a Virtual Machine Scale Set (VMSS), all instances within that scale set must belong to the same proximity placement group. In this scenario, VMSS1 is already associated with Proximity2. Therefore, to maintain the co-location and low latency benefits for all instances within VMSS1, you must continue to use Proximity2 for any new assignments or modifications related to VMSS1. Using Proximity1, Proximity3, or a combination including them would either separate instances of VMSS1 into different proximity groups (which is not allowed for a single VMSS) or introduce unnecessary complexity and potential latency issues.