You can't have a mix of AND+OR with several combined conditions, you probably need to use a boolean variable:
Is button1 up
Is button2 up
Is button3 up
Is button4 up
If b then .........
But if you are comparing some property that can be accessed in expression, or an instance variable, then you can do it in one line:
if ((Button1.isUp & Button2.isUp) | (Button3.isUp & Button4.isUp))