Correct me if I'm wrong, but if I owned 100k ZCash, and proposed a fork like this, would I instantly have 100k YCash?
So people could just keep forking chains to give themselves more coins? Even if YCash was only valued at 30% the price of ZCash, that's basically an instant 30% profit?
Are you just arriving in crypto country? 90% of the coins out there are either code- or chain-forks (and a whole lot of useless ERC-20 tokens too).
Ever heard of Bitcoin Cash, Bitcoin SV, Bitcoin Gold, Bitcoin Diamond, Ethereum Classic...? Airdrops?? Suit yourself, have a look at the top 25 on CMC.
You're most welcome to do your own coin if you want to and you have 5 minutes!
https://forkgen.tech/ 
Anyway... It's unlikely that a "simple" fork reaches one third of the value of the original asset just like that. There just already to many with no added-value whatsoever. The market is essentially saturated.
That being said, whales can always make money out of it, for sure.