...Zeroknowledge coins require a "trusted set up". We need to be absolutely sure we can trust whoever set it up...
From the first paragraph of the Zcoin section:
Since monetary inflation of any kind would be detected immediately this also mitigates any trust issues during initial setup.
According to the interview with Gary Le Zcoin does have a trusted setup.
Just after the 30 minute mark or thereabouts.
Unless I missed something
http://www.cryptoholics.com/cryptoholics-ep02/Zcoin uses a number from the
RSA factoring challenge from like 1991 as their trusted setup parameter (RSA has recently been revealed to be in bed with the NSA, but this was 20 years before that). For some reason Zcash requires a much more complex trusted setup that can't just be the product of two prime numbers, and so there was the whole Zooko and Peter Todd fiasco.
The other thing to consider is that the money supply is known in the case of Zcoin, so if someone managed to factor the RSA 2048 number and people noticed the money supply was bigger than expected, than Zcoin could just fork I think. With Zcash there is no way to no if someone is minting coins due to a flaw in the setup.
I am not a mathologist or cryptotician, take it with a grain of salt.