The first cure is found inside a shack, held by a Blue Umbrella soldier corpse. Once used on Zoe in Joe's house, this will trigger a cutscene.
The second cure is located inside a paddle boat. As the item is taken, this will trigger a cutscene where Joe is ambushed by the Swamp monster. This cure can be used on Zoe inside the Baker's house, after defeating the Swamp monster.