Brackets in chemical formulas
$\ce{2Zn(NO3)2}$ can be interpreted differently, depending on the context.
The '2' outside of the parenthesis could either refer to two molecules or two moles of substance. In either case, the chemical formula tells you the same thing: that there are two units of $\ce{NO3-}$ for every unit $\ce{Zn^2+}$.

I would write it as zinc (II) nitrate, (read as 'zinc-two-nitrate) The roman numeral (II) refers to the oxidation state of the zinc ion, which is $+2$.