Only x and y appear on the expression so perhaps z is the value of the expression? It's not clear whether only integer values of x, y and z are implied, so we'll assume that at least x and y can take values separated by 0.5. We'll use values: 0<x<1, -1<y<1.5. The range of values for x has been halved because x^2 and abs(x) only the only terms containing x and both terms produce the same vales regardless of the sign of x. Let v=x^2+(y-x)^2, then the expression becomes: 2+(-sqrt(1-v)cos(30(2-v))).
I'll show the pairs of x and y values as (x,y) and the resultant v:
(0,-1): 1; (0,-0.5): 0.25; (0,0): 0; (0,0.5): 0.25; (0,1): 1; (0,1.5): 2.25
(0.5,-1): 2.5; (0.5,-0.5): 1.25; (0.5,0): 0.5; (0.5,0.5): 0.25; (0.5,1): 0.5; (0.5,1.5): 1.25
(1,-1): 5; (1,-0.5): 3.25; (1,0): 2; (1,0.5): 1.25; (1,1): 1; (1,1.5): 1.25
Putting these values of v into the expression I'll show the results as (v,expression):
(1,2); (0.25,1.4728); (0,1.5); (2.25,E); (2.5,E); (1.25,E); (0.5,1.5); (3.25,E); (2,E).
E signifies an error (square root of a negative number).