Tough one to answer my friend. Lisinopril is an ACE(Angiotensin converting enzyme) inhibitor which blocks the enzyme from converting into its active form Angiotensin II. This is part of the bodies blood pressure regulatory mechanism which causes narrowing of blood vessel vasculature, as well as holding onto fluid limiting urine formation in the kidneys. The end result is an increased blood pressure. This medication limits both of those pathways lowering your blood pressure accordingly.
The addition of HCTZ(hydrocholorthiazide) or a thiazide diuretic helps to control blood pressure even further by enhancing the diuretic effect of excessive intravascular fluid.
While creatine tends to draw intravascular fluid(in the veins/arteries) into both the interstitial and intra-cellular regions, it's still a risk at increasing your overall blood pressure in many ways. I'm not sure i would recommend it, however again, i'm not a doctor.
IMO, it runs a great risk to be counter-productive my friend. If it concerns you though, ask you doctor about it. However, i think he's going to tell you what i already have.
Your health comes first my friend. Be safe.