What happens when you combine ACE and ARB?

Can you elaborate on the effects of combining ACE inhibitors and angiotensin receptor blockers, also known as ARBs? How do these two classes of medications work synergistically, if at all, in treating conditions such as hypertension and heart failure? Are there any potential side effects or precautions that patients should be aware of when using these medications in combination? Furthermore, is there any research that supports the superiority of this combination therapy over monotherapy in specific medical scenarios?