Complex sentence: Rounding the final mark she held a six second lead, but here Dickson made one of the rare mistakes of his summer and struck the mark, forcing "KZ 7" to round again and ending all hope they had of winning the race.
Split into simpler sentences: Rounding the final mark she held a six second lead, but here Dickson made one of the rare mistakes of his summer by striking the mark. The error required "KZ 7" to round again, and the resulting time loss ended all hope the New Zealanders had of winning the race.