The only way cloud mining like this would ever make sense would be either if the cloud miner has a huge competitive advantage ( i.e. proprietary software that greatly outperforms existing available implementations) or if there is a huge disequilibrium between the market price and the hashrate.
Most of these contracts were sold on the basis that such proprietary software existed and whilst this advantage may have been true almost right up to launch it almost definitely no longer holds.
There certainly was a huge disequilibrium between market price and hashrate at launch but ironically almost all cloud providers had an issue making timely payouts during this time. It’s unlikely we ever see such a situation arise again which is why it’s almost certainly best to buy ZEC instead of investing in cloud mining. If you want to mine then the only realistic option is to do it yourself. If it isn’t feasible to mine yourself (say due to electricity costs) then just buy the ZEC!
edited to add that is is of course possible to achieve a positive ROI from cloud mining but that is more a function of the underlying ZEC rising and almost nothing to do with the cloud provider.