How does lisinopril and hydrochlorothiazide treat high blood pressure?

Lisinopril-hydrochlorothiazide (HCTZ) is a combination drug that treats people with high blood pressure, or hypertension, two ways. Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor, which relaxes blood vessel walls and lowers blood pressure. Hydrochlorothiazide, a diuretic, helps remove salt and water from the body to decrease blood volume and lower blood pressure.