mass molar of zinc hydroxide Zn(OH)2 = 99.424 g/mol
1 mole ----------> 99.424 g
mole ----------> 0.9876 g
mole = 0.9876 / 99.424
= 0.00993 moles of Zn(OH)2
1 mole ------------> 6.02x10²³
0.00993 ----------> units
units = 0.00993 * 6.02x10²³
= 5.977x10^21 formula units.
hope this helps!.