Complex sentence: It was then inscribed on the World Heritage List under the following criteria (ii) and (iv) with the assurance apart that from creating a buffer zone under the declared heritage site with a buffer zone, the steam trains would be retained within the site.
Split into simpler sentences: It was then inscribed on the World Heritage List under the following criteria (ii) and (iv). An assurance recorded was that apart that from creating a buffer zone under the declared heritage site with a buffer zone, the steam trains would be retained within the site.