To run HyperV in ESXi modify the vmx file of the HyperV guest vm:

vhv.enable = "TRUE"
hypervisor.cpuid.v0 = "FALSE"

To allow network communication from VMs on the HyperV over the HyperV virtual switches to the ESXi network the "Promiscuous Mode" of the ESXi network switch has to be set to "Accept" - ESXi-Host => configuration => networking => select vSwitch<X> => properties => select vSwitch => Edit => Security => Policy Exceptions => Promiscuous Mode => Accept

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