Azure Hybrid Benefit doesn't impact Nested VMs. If you are using Azure Hybrid Benefit you will get the discount on the base OS but still need to follow the licensing requirements for any nested VMs.
Windows Server Standard edition includes two free licenses for nested VMs. Datacenter edition includes unlimited licenses for nested VMs. Windows Server Azure Datacenter edition does not include free virtualization.
If you have Software Assurance, you can utilize the Hybrid Benefit and deploy multiple VMs instead of running nested VMs. The calculator here should give you more details.
If you still have questions our sales team can help, you should be able to chat directly with them. Hope this answers your question!
https://azure.microsoft.com/en-us/pricing/hybrid-benefit/#overview
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