So the cheapest way to get Bitcoin Private is probably to buy ZCL? Unless I believe Bitcoin Private will drop under current ZCL prices.
That is correct. And that's the reason for the recent price rise in ZCL.
I am on the edge of buying ZCL but not so sure about it. I believe that the price of ZCL will drop heavily even before the snapshot. To me personally this is a super risky gamble. And the ZCL devs already said that it is unclear how ZCL as a network will proceed afterwards. So the whole buying activity is because of the fork but someone might play it even smarter. Most likely the people who started buying at 3-4 dollars are now slowly selling into the demand up to 150 dollars.