Oxidation states of X, Y, Z are +2, +5 and -2 respectively. The formula of the compound formed by these will be

We know that the algebraic sum of the oxidation states is always zero in neutral compound. Oxidation states of X=+2                                  Y=+5                                   Z=-2So, the algebraic sum of X, Y and Z should be equal to zero which is found in XY2Z6.XY2Z6=+2+(5×2)+(-2×6)               =+2+10-12-0