ZenCash network was hit with 51 percent attack yesterday, on June 2nd 2018 at 0243H UTC. The ZenCash team did mitigation steps to increase the difficulty of future attack on its network and safeguarded its network. However, around 6600 ZEN and 13000 ZEN for double spends were done and attacker was able to reorganize more than 30 blocks. This means the attacker knew what he was doing.
ZenCash team says that it will continue to monitor the network and do forensic analysis on the exchanges that are affected with it.
In little less than a month, three big cryptocurrencies that make use of PoW algorithms have been attacked using 51% method. This includes Bitcoin Gold, Verge and now, ZenCash. That being said, algorithm leaders such as BTC, LTC, XMR, ZEC are fine. Other PoW coins are exposed to 51% attack, any minute.