Yep, I've missed apostrophe's quite a few times. It's was a common cause of infinite loops for me in the past, but I suppose I've trained myself to spot them more quickly.

Perhaps zip can be more simply explained by a simple example:

    out: zip ["a","b","c"] [0,1,2]
    out: [("a",0),("b",1),("c",2)]

    out: fmap fst [(0,1),(2,3),(4,5)]
    out: [0,2,4]

    out: fmap snd [(0,1),(2,3),(4,5)]
    out: [1,3,5]