Reduction of Organic compounds
I will try to explain the difficulty of this problem by using a simpler reaction, the reduction of nitrobenzene, which is already difficult enough. The reduction of dinitrobenzene should produce more different possibilities.
Nitrobenzene can be reduced into at least five different compounds. It depends on the choice of the reducing agent. I am afraid nobody can justify the particularly mechanisms used by a given reducing agent to get to each final result.
With ($\ce{Sn + HCl}$) or with ($\ce{Fe + HCl}$), it gives aniline, $\ce{C6H5NH2}$.
With sodium methoxide ($\ce{NaOCH3}$), it gives azoxybenzene, $\ce{C6H5N(O)NC6H5}$
With zinc, it can produce three different products:

With zinc + $\ce{NH4Cl}$ at elevated temperature, it gives
phenylhydroxylamine, $\ce{C6H5NHOH}$.

With zinc and an alcoholic solution of $\ce{NaOH}$, it gives azobenzene
$\ce{C6H5N=NC6H5}$.

With zinc and an aqueous solution of $\ce{NaOH}$ at $\pu{60 ^\circ C}$, it give hydrazobenzene $\ce{C6H5NH-NHC6H5}$.