Complex sentence: However, this worked both ways; zamindars became a naturally conservative interest group and once British policy changed to one of reform and intervention in custom in the mid-nineteenth century, they were vocal in their opposition.
Split into simpler sentences: However, this worked both ways; zamindars became a naturally conservative interest group. Once British policy in the mid-nineteenth century changed to one of reform and intervention in custom, the zamindars were vocal in their opposition.