Zcash no balance after mining for four days - normal?

I'm new.
I have four PC's .. intel core duo's ~2.0GHz .. that have been mining for four days now ... I still don't have any balance.
Is this normal? When might I expect to find something?
Thanks

Solo mining is very difficult to mine a block...

You have to connect some pool to mine blocks.

Can someone suggest a good Pool for Claymore's CPU miner?

I use nanopool. There are others as well.