Complex sentence: Hastings on its own is New Zealands 8th largest urban area and if it were to amalagamate with Napier it would become New Zealands 5th largest urban area.
Split into simpler sentences: Hastings on its own is the 8th largest urban area in New Zealand. If it were to amalagamate with Napier it would become New Zealands 5th largest urban area.