Look at main() and only main(). You set the number and total of pizza, wings and bread to zero. Their values never change. 0 * anything = 0. You seem to be trying to calculate with these values before you have set them to anything.
The comment from abellia confused you somewhat, huh? ;)
Nono it's pefectly ok to initialze the variables. If you leave your ...Num variables 0 then the ...Total variables will be 0 as well (the same applies for unitialized).
So you have to ask the user how many pieces he want before you're calculating the result (...Total) and not after (like in displayResults()).