Looks like the developer there's no truly ASIC resistant PoW algorithm and it's only matter of time until ASIC manufacture create another one, especially if they only slightly tweak it's PoW algorithm just like Monero which is extremely difficult.
But if they don't care about significant network hashrate change or don't care about hard-fork, then it shouldn't be difficult task for developer.
I suggest OP read this article (
ASIC Resistance is Nothing but a Blockchain Buzzword), then you might understand their decision.
ProgPow
Yes, ProgPoW is the best we currently have against ASICs and while nothing is truly ASIC proof it would buy a significant amount of time to hold off massive ASIC farms until further improvements can be developed.
I feel the real reason most of these teams are deciding against making any changes to the algo is lack of knowledge in the area. As much as they spout off about how great their version of a copy/paste coin is from its derived parent, they really have little to no real coding skills.
It is fairly trivial for anyone with even a passing interest in programming to copy/paste a coin's code from Github and create their own derivative from it. Simple name changes and adjusting a few well understood parameters means you can superficially create a new coin, but at its heart it is still chained to its parent code base.
I myself have created about a half dozen workable forks from various coins simply for learning and experimenting, and could have easily launched yet another worthless shitcoin to the world if I had wanted. Most of these similar types of coins will update their code only once the parent code base is modified for any non-superficial changes.
For real changes such as modifying the underlying mining algo, requires a much deeper understanding and also breaks them away from their safety line of being just able to fork from the main parent anytime a significant security or other change is required.
Anyway, I have personally began to sell off and limit my exposure to many of these me-too coins, Zencash included, as I really do not see a future for them once the initial euphoria has wore off, and I think the euphoria is running out fast with the current bear market. Once the overall crypto market does recover, I think the only coins that will significantly rise again will be the unique or main coins, BTC, ETH, ZEC, Monero, etc and all of the clones will stay at low prices and eventually become worthless as they bring no real meaningful contribution to the space.