The partial derivative d ^ Z / DXDY of Z = f (XY, y)

The partial derivative d ^ Z / DXDY of Z = f (XY, y)

From the title,
z=f(xy,y)
So,
dz/dx=f1(xy,y)*y
and
d²z/dxdy
=d(dz/dx)/dy
=d(f1(xy,y)*y)/dy
=f1(xy,y)+y[f11(xy,y)*x+f12(xy,y)]
=f1+xy*f11+y*f12
Where f (U, V) is F 1 for u and F 2 for y