I have roughly sketched a proposal which I am thinking will ameliorate the energy problem, remove the selfish mining attack (because mining becomes unprofitable), fix the block chain scaling, and Tragedy of the Commons around verification asymmetry for PoW (which is Ethereum’s insoluble dilemma). It is in the thread I provided a link to previously, but I will point you to a more specific post that gets more direct to the economic math point (though one would still need to read the context of prior and subsequent posts of the thread):
However, this design may not work for Zcash, because Zcash has higher verification costs (but that is not a problem if the verification cost is still insignificant relative to the typical transaction values) and because the rate of transactions might be much more infrequent than the microtransactions market I was designing for (however if Zcash can be widely used then transaction rate may be sufficient and also the PoW share submitted with each transaction can be much higher than in my design because I assume anonymous transactions can be for much higher minimum values).
There may or may not be another hindrance with the fact that Zcash’s block chain is afaik monolithic and amorphous, but I haven’t thought through that issue yet.
Afair (and I don’t have time to re-read it given all I have learned since I first read it) that paper did not articulate the most unarguable and salient reasons that PoS is inferior. I think we furthered the understanding in my linked thread. Also I wrote something about this in one of Vitalik’s threads: