Lad off here bred some lab x Lurchers a couple of years back. They looked nice things. No reason why it shouldn’t work. A lot of people use 1/2 crosses of various types. If you get the right lab and a decent greyhound then I think they would make a decent worker. My mate has a dog that is 1/4 GWP x lab. Uses it for most things, beating, picking up,wildfowling. I’d take a chance if that went over a decent greyhound.