Instrumental optics and slit configurations play a major role in defining the quality of powder X-ray diffraction (XRD) data. In this study, the effect of divergence slit and Antiscatter Slit variation on XRD pattern was systematically investigated using a PANalytical Empyrean X-ray diffractometer equipped with Bragg-Brentano HD (BBHD) optics and fixed divergence slit (FDS) optics, using zinc oxide (ZnO) as an experimental sample. Divergence and anti-scatter slits were varied, while all other instrumental parameters, including scan conditions,were kept constant, enabling a controlled and reproducible methodological comparison. The diffraction data were quantitatively analysed in terms of background intensity (IB), highest peak intensity(IP), peak-to-background intensity ratio (IP/IB), and full width at half maximum (FWHM). The results demonstrate that divergence slit selection strongly influences background and peak intensity, while relatively marginally influencing FWHM, revealing a clear trade-off between intensity and resolution. Using optimum slit configuration and BBHD optics we identified the zinc oxide phase from the crystallographic open database (COD) with high degree of accuracy. On the basis of this study, we are providing a practical approach for optimizing instrumental settings for reliable phase identification.