As per the law of definite proportion a chemical compound will always contain the same elements that combine together in the same ratio by mass.
In case 1:
Mass of Zinc sulfide sample = 100 g
Mass of Zn = 67.1 g
Mass of sulfur = 32.9 g
Ratio Zn : S = 67.1 : 32.9 = 2:1
In case 2:
Mass of zinc sulfide formed = 1.77 g
Mass of Zinc taken = 1.19 g
Mass of sulfur = 1.77 - 1.19 = 0.58 g
Ratio Zn:S = 1.19 :0.58 = 2:1
Since the ratio in both cases are the same, the data is in agreement with the law of definite proportion.