@gerlig is your dizziness just when standing from sitting or from supine to standing or to sitting position or is it all the time? I’m on Lisinopril 10mg for over 20 years with excellent results. You have a water retention issue which is why the HCTZ with the Lisinopril. You could be low on fluid unless you’re on fluid restriction?
Make sure when you go to change any position like sitting or standing don’t do it suddenly. Sit-up from laying position and wait for a 10 count before standing so your blood returns to your head. You also might need a reduction in dose too.