Pressing 2 keys/mousebutton at same time, not working

Im trying to make a event happen when pressing mouse button 0 and 1 at the same time.
if(Input.GetMouseButtonDown(0) && (1))
But it doesent work. I have tried other combinations as:
if(Input.GetMouseButtonDown(0) && Input.GetMouseButtonDown(1))
I have also tried with keys, but it still doesnt work.

How can i press the two mouse buttons at the same time and make a event happen?
Or is this a bug that needs to be fixed?

What I understand is that you want to make an event happen when both buttons are clicked. If so, then try this:

if(Input.GetMouseButton(0))
{
  if(Input.GetMouseButton(1))
      //Do your event here, what should happen is that if you 
      //press MouseButton 0 then MouseButton1, an event will
      //happen
}

I use this format in my movement script as well, and it works properly. Hope this helps, and ask me questions if needed.