Is your genproclimit set equal to 6? You will likely be solving faster at 6 cores, but you will eventually have to deal with the law of diminishing returns relative to the # of cores you’re using when mining Zcash. Best way to do find out is to test with your hardware with:
time ~/zcash/src/zcash-cli zcbenchmark solveequihash 10
This returns the # seconds to complete the equihash algorithm ten times. This will get you pretty good info for now. You can set it to a higher number, e.g. 20 to get a more accurate average.
See this thread for more info
If you do test, it would be great if you could post your results here: https://benchmark.minezcash.com/index.php?title=Main_Page