Rinse salmon fillets, pat dry, and set aside. Melt 2 tablespoons of the butter in a skillet. Meanwhile, cut the zucchini into chunks for steaming. Steam until very soft, about 15 minutes. Panfry the salmon in the skillet, searing it on the outside. Keep salmon warm. When zucchini is soft, blend in blender with remaining 2 tablespoons of butter and chopped parsley. Serve salmon on shallow plates, with zucchini puree around it. Season to taste and garnish with additional parsley.