We have,

a = 0.27nm = $0.27 \times 10^{-9}$ m.

A = 65.37

As Zn has HCP structure,

we know, 

$3 \sqrt{2} a^{3} \rho = n \dfrac{M}{N} $

where M= Atomic weight of Zn, N= Avagadro's number= 6.023 \times 10^{23} 

Mass=$ n \dfrac{A}{N}$

$=6 \times \dfrac{65.37}{6.023 \times 10^{26}}$

$=6.512 \times …