Configure Nested Virtualization
Step 1: While the virtual machine is in the OFF state, run the following command on the physical Hyper-V host, in this case on SRV1. This enables nested virtualization for the virtual machine.
Step 2: Set-VMProcessor -VMName <VMName> -ExposeVirtualizationExtensions $true In our case: Set-VMProcessor -VMName VM1 -ExposeVirtualizationExtensions $true Step 3: Start the virtual machine.
Install Hyper-V within the virtual machine, just like you would for a physical server.
Enable the Hyper-V role through Settings
Step 4: Right click on the Windows button and select 'Apps and Features'.
Step 5: Select Programs and Features on the right under related settings.
Step 6: Select Turn Windows Features on or off.
Step 7: Select Hyper-V and click OK.

When the installation has completed you are prompted to restart your computer.
Reference:
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/user-guide/nested- virtualization
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/quick-start/enable-hyper-v