Complex sentence: Within New Zealand, Betis remnants caused flooding and mud-slips, which led to several roads being closed, while a helicopter and its pilot were were lost at the height of the storm, while they were traveling from Napier to Gisborne.
Split into simpler sentences: Within New Zealand, Beti's remnants caused flooding and mud-slips, which led to several roads being closed. A helicopter and its pilot were were lost at the height of the storm, while they were traveling from Napier to Gisborne.