zksnark in Ethereum is just an option. In Monero it is specialisation.
If I would need some sort of privacy I definetly will use Monero instead of other coins.
Also I still confused about possible backdoor in Zcash and zkSNARK technology
https://bitcointalk.org/index.php?topic=2011221.0
Especialy after dark markets was busted by feds shortly after adding Zcash as payment method. Coincedent? I am doubt peoples who seriously worry about their privacy will use something like this after all being said.
ZKsnarks are a type of cryptographic proof. you can read about it here: https://en.wikipedia.org/wiki/Non-interactive_zero-knowledge_proof The backdoor in zCash might exist in more than one place, but I think the major one that people wonder about is the setup seed, which is talked about in the link. I guess the same question could be asked of the setup seed on the ethereum network as well. Does any one have some insight into this?