I've activated Windows Server 2012 on Hyper-V virtual machine (guest) and i want convert it to VMware virtual machine on ESXI server
My question is
"Can i do it without activate Windows again ?"
No. The underlying virtual hardware seeing by Windows Server will have changed too much, requiring reactivation.
If you were moving between Hyper-V hosts or ESX hosts you could avoid it by exporting the guest and importing it on the destination. But between different hypervisors? Not that I know of.