Why could i not mine eth ? i was about to mine eth as long as possible then switch to zec
The DAG has grown to a size where you need at least a 4GB card to mine.
Also, the 7970 does very low hashes for the wattage consumed. ZEC should be your target coin right now.
ETH is still mineable on 3GB cards - but the 7970 is a lot better off mining ZEC at this time.
1070 is also not a good choice for ETH mining, does better on ZEC - but it's been very close at times the last couple weeks.
There are other altcoins that the 1070 does better at, look into the skein and groetsl coins, or try Nicehash to see other options.