\preauthor{\begin{flushright} Not align with \begin{flushleft}

For my cover i need to have the right part of the text aligned with the left part, but it's not happening, Here i link my code and the image can you please help me out?

\documentclass[10pt,showtrims,a4paper,twoside]{memoir}

\input{structure.tex}

%------------------------------------------------
% Thesis Information

\title{Un Modello per la Rappresentazione della Semantica di Diagnosi Cliniche \Large \newline \newline \centerline{Tesi in} \newline Data Management}

\author{Luigi Vecchione}

\date{18 Luglio 2016}

\newcommand{\institution}{University degli Studi di Salerno\xspace}

\newcommand{\department}{\centerline{Dipartimento di} \newline Scienze Aziendali - Management \& Innovation Systems\xspace}

%------------------------------------------------
% Fonts

\renewcommand*{\acffont}[1]{{\normalsize\itshape #1}}
\renewcommand*{\acfsfont}[1]{{\normalsize\upshape #1}}

%------------------------------------------------
% Hyphenations

\hyphenation{a-no-ma-lous a-no-ma-ly amounts breaches}

%----------------------------------------------------------------------------------------
%   TITLE PAGE
%----------------------------------------------------------------------------------------

\renewcommand{\maketitlehooka}{
\centering
\includegraphics[width=2.5cm]{Figures/logounisa}\\[.5cm]
\institution\\
\emph{\department}\\[.2cm]
Laurea Magistrale in Tecnologie Informatiche e Management
\par
\hrulefill
\vfill}
\renewcommand{\maketitlehookb}{\vfill}
\renewcommand{\maketitlehookc}{
\vfill
\begin{flushleft}
Relatore:\\
\textbf{Prof. Giuseppe Polese}\\[.3cm]
\end{flushleft}
\vfill}
\renewcommand{\maketitlehookb}{\vfill}

\preauthor{\begin{flushright}Autore Tesi:\\\bfseries}
\postauthor{\end{flushright}}


• Welcome to TeX.SX! Your code isn't compilable and there's no image – user31729 Jun 4 '16 at 14:58
• Thank you Christian i were just editing it, i have some connection issues, but thank you for your help anyway. :) – LuigiVe Jun 4 '16 at 14:59
• Yes, but we still can't compile it -- we don't have structure.tex – user31729 Jun 4 '16 at 15:02
• I wonder if the original file has a license? – Johannes_B Jun 4 '16 at 15:02
• @ChristianHupfer Don't be silly. structure.tex directly leads to l-templates.com ;-) – Johannes_B Jun 4 '16 at 15:02

You can do all kinds of stuff, for example forget about all the hooks and do the following.

\renewcommand{\maketitlehooka}{
\centering
\includegraphics[width=2.5cm]{example-image}\\[.5cm]
\institution\\
\emph{\department}\\[.2cm]
Laurea Magistrale in Tecnologie Informatiche e Management
\par
\hrulefill
\vfill}
\renewcommand{\maketitlehookb}{\vfill}
\renewcommand{\maketitlehookc}{\vfill}
\author{\parbox{\textwidth}{Relatore:\hfill Autore:\\\textbf{Professor}\hfill\textbf{Student}}}


Though i would set up my titlepage completely by hand, as seen in How to customize my titlepage?