The Nikon Z pre-orders will open at 3 am EST. Here are the links you can use (the Australian links are already live):
As I already mentioned, if you are considering to purchase the new Nikon Z6 or Z7 cameras, I suggest you put your pre-order in tonight, maybe even with multiple stores, you can always cancel it later. This is what I will do. I expect the new Z cameras to be out of stock for months.
Nikon AF-S NIKKOR 500mm f/5.6E PF ED VR lens pre-order links: