Line 1: Either Z or 7 is correct, but neither is in the right position
Line 2: I guessed Z, and put it in another position which turned out to be correct. E is also correct, but I'm not sure which position is right.
Line 3: E is in the wrong position (white dot), 8 is eliminated.
Line 4: I've nailed E and Z, one of the S's is in the right position.
Line 5: S, E, and Z are in the right positions, either F is in the right position.
Line 6: (SEZFJ) I tried the J now, in the last position. I now know that I have all the correct letters/numbers, and I know that F in the last position must be correct.
Line 7: Bingo!