In the sample image, it looks like Z = U, i.e., the color of the surface corresponds to a U-value which is equal to the Z-value of the surface. That's not the case here, since here the variable z is not equal to the variable u.
Nevertheless, you can create a surface that uses x, y, and z as its spatial coordinates and u as its color.
x=[1;2;3;4;5;6];
y=[20;40;60;80;100;120];
z=[7.5 6.4 5.4 4.7 4.6 7.3
8 7 6.3 5.9 6.2 9.3
7.6 6.9 7.6 10.6 17.8 38.8
8.9 9 10.8 15.1 24.6 52.2
9.9 10.4 12.5 17.2 27.4 57.6
11.8 12.9 15.6 21 32.6 67.2
];
u=[1.166095944 0.97358166 0.779831701 0.585208118 0.390139923 0.194918905
1.125081616 0.938075367 0.750416267 0.56248955 0.374665613 0.187071512
1.299656109 1.085162773 0.869349505 0.6528042 0.435361439 0.217700286
1.33599592 1.114982352 0.893254036 0.670663527 0.447356191 0.223576511
1.353130634 1.129064616 0.904218619 0.678721998 0.452633899 0.226149653
1.383264964 1.153932529 0.923799929 0.693105559 0.462123411 0.230823789
];
% hard to say which one of these four is the correct way to depict
% these data:
surf(x,y,z,u);
% surf(x,y,z.',u.');
% surf(x,y,z.',u);
% surf(x,y,z,u.');
cb = colorbar();
xlabel('X')
ylabel('Y')
zlabel('Z')
ylabel(cb,'U','Rotation',0);
