Quick Create using existing VHD makes a copy of the VHD the VM it originally belongs continues to be the sole owner and user of the original VHD, new VM uses a copy of it created by Quick Create. Of course it has always been possible to create a new VM using an existing VHD, but in case user selects a VHD belonging to another existing VM, both virtual machines will be using the same VHD which can be quite confusing. Quick Create also allows user to create a new virtual machine using an existing virtual hard disk file (VHDX or VHD). See also: Create a Virtual Machine with Hyper-V | Microsoft Docs (OK, I admit: creating a new VM will really take just a few seconds but as Quick Create is still a preview like the build it was introduced in, the VM created is usable only after 'pimping' it a bit, changing default specifications.) Run Quick Create, name the VM, select installation source and virtual switch, go! With it you can create a new virtual machine (VM) literally (yes, literally!) in seconds.

One of the new cool things is a new feature in Hyper-V Manager called Quick Create. Windows 10 Insider Preview Build 15002 gave a facelift to Hyper-V as told earlier on Ten Forums.

Creating vm in hyper v