You are not supposed to extract part 2. People, please read the instructions. You should have part 1 and part 2 in the same folder. Once they have both been completely downloaded, right-click on part 1 and choose 7-zip > 'Extract here'. That rebuilds the original resources archive. Delete the parts, and add that one to an OMOD. Then, proceed as usual. Please, in the future, post in the relevant mod's thread, and read the description on the TESNexus page for installation instructions as well. Ismelda even created a guide with screen shots for this...