I don't think it makes any sense to try to compare the efficiency of different proof of work systems. Now you could compare the work that goes into synchronizi

I don't think it makes any sense to try to compare the efficiency of different proof of work systems. Now you could compare the work that goes into synchronizing the blockchain between all nodes, but I'd expect that has a near-negligible environmental impact compared to all of the miners. (Individual Zcash transactions are a bigger file size than individual Bitcoin transactions if I remember right.)