One thing some people often fail to do is separate mining and investing/trading. They are two completely different activities. There are various exchanges and services for converting one coin into another. Maybe people are too confused or lazy to figure out how to convert crypto or think it's too much trouble. It isn't and the transaction fees are really not that significant compared to what you would lose by mining a currency with a good future, but bad mining profitability.
Choose which coin to mine based on the max value you can convert to fiat currency. That should be your only consideration.
Then you can convert your mined coins or cash into whichever coins you want to INVEST in based on what you think the future of those coins.
Simple example:
Assumptions:
One day of mining (today)
Ether price today = $200
Zcash price today = $200
Ether price next year = $400
Zcash price next year = $250
Mining Ether rate today = $17/day
Mining Zcash rate today = $20/day
If you "mine and HODL" ETH for 24 hours, you'd get $17 in ETH and it would be worth $34 next year.
If you "mine and HODL" ZCASH for 24 hours, you'd get $20 in ZCASH and it would be worth $25 next year.
HOWEVER, if you MINE ZCASH for 24 hours and convert it to ETH, then you'd end up with $40 next year.
THAT'S what you need to do: MINE what's most profitable NOW and INVEST your mined coins in whichever coin you think will increase the most in the future.
Current mining rates on these two coins may be pretty similar, but they could potentially be VERY different. In fact, the best coin to invest in may not even be minable at all.
Good luck figuring out which coin will increase the most in the future. As anyone can tell you, it's just another form of gambling...not much different from the equity, commodity, and fiat currency markets.
You're assuming that both Ether and Zcash will continue to rise for a year. It's not that certain, as ETH is in a bubble that can really hurt people. I don't believe it will keep going up, since it's peaking now. There has to be a downtrend at some point, like there was in Bitcoin in 2014.
If you're asking about mining, I think GPU is too difficult to handle in a typical home environment. Too much power drawn, noise and heat. I'm interested more in CPU and HDD coins.