I'm having trouble figuring out how to manipulate two arrays. The arrays are listed below.

double z1[2];

double z2[2];

z1[0] = a;

z1[1] = b;

z2[0] = c;

z2[1] = d;

*where a,b,c, & d are user inputs. I need to do different operations as separate functions (i.e. adding, subtracting, dividing, multiplying) and then output the results into a separate array. Any help would be greatly appreciated.