Mining Difference with Multiple Rigs between Bitcoin and Zcash I try to understand how the mining hardware environment is different between Bitcoin when centralized mining ecosystem is more encouraged compare to Zcash or Ethereum where pooling is more encouraged.

So is it true that when you have 2 separate rigs mining bitcoins, each individually not joining a pool, they could compete with each other, as oppose to mining Zcash or Ethereum, the 2 rigs join forces to mine together 
in the same pool?
regards
There is no difference between bitcoin and zcash here, mining with multiple machines work the same way.

If you have 2 machines they can mine in the same mining pool or separate pools. You choose.

Your machines are never competing against each other. You are the one that get paid for the work of both machines.

If you are solo mining instead of using a pool, the machines are still not competing against each other. They are both trying to find a block for you, the owner.

The bad thing you want to avoid is having both machines do the exact same work. That would be a waste. The second machine wouldn't be doing anything useful. Handing out duplicate work would be a serious fault in the mining pool software.