Y and Z are, respectively: N2O5 and HPO3, N2O4 and HPO3, N2O4 and H3PO3, N2O3 and H3PO4

Upon heating KClO3 in the presence of a catalytic amount of MnO2, oxygen gas (W) is formed. Excess amount of oxygen gas (W) reacts with white phosphorus to give tetraphosphorus decaoxide (X). The reaction of tetraphosphorus decaoxide (X) with pure HNO3 gives HPO3 and N2O5. Thus (Y) and (Z) are HPO3 and N2O5 respectively.

2KClO3 →MnO2 3KCl + 3O2 (W)
P4 + 5O2 (W) → P4O10 (X)
P4O10 (X) + 4HNO3 → 4HPO3 (Y) + 2N2O5 (Z)