That is basic principle why miners should choose different pools to mine in order to help maintaining healthy status of blockchain networks.
However, the recent attacks on BitcoinGold network maybe due to its small total hashrates and easily be dominated by a bit large mining farms.
Here's a thought: If a 51% attack were to occur on Zencash like it did on Bitcoingold (same Equihash algo)
In my point of view, this is also basic and important functions of secure nodes (and masternodes, in other crypto coins). Those ones will help to make networks more secure, stable and reliable.
if the same attacker or someone else with huge Equihash hash power decided to target Zencash, where would the secure nodes come in? Would they prevent such an attack, make an attack harder/more expensive to execute or not at all?