45, perimenopause, taking zestorectic (10/12.5mg). 5-7 mile walk/run 5 times a week. Ldl=42.Developed palpitations only when sitting. Zestorectic? Peri?

Hard to say. The best way to diagnose palpitations is to record them. Your doctor can prescribe a monitor that you can wear which will allow your heart rhythm to be recorded. The recorded rhythm during your symptoms will be very helpful in getting to the bottom of it.
It depends. Not clear. Zestoretic (lisinopril and hydrocholorthiazide) can cause problem because of BP or electrolytes. Peri menopausal syndrome often has vasomotor symptoms. Neither is likely to cause problems only when seated but the menopause is more likely to have rest related symptoms.