Fit multiple data set

Hi, I have been searching around for how to fit several data set to the same function but without any luck, as my problem is specific. So here goes.

I have a matrix with the following columns: x1 y1 z1 x2 y2 z2 x3 y3 z3 so I have a 500x9 matrix. I want to fit these values to a surface. I know how to seperatly fit each (xi,yi,zi) data set but how would one do it simultaneously?