  A search for heavy neutral Higgs bosons and $Z^{\prime}$ bosons is performed
using a data sample corresponding to an integrated luminosity of 36.1 fb$^{-1}$
from proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the ATLAS
detector at the LHC during 2015 and 2016. The heavy resonance is assumed to
decay to $\tau^+\tau^-$ with at least one tau lepton decaying to final states
with hadrons and a neutrino. The search is performed in the mass range of
0.2-2.25 TeV for Higgs bosons and 0.2-4.0 TeV for $Z^{\prime}$ bosons. The data
are in good agreement with the background predicted by the Standard Model. The
results are interpreted in benchmark scenarios. In the context of the hMSSM
scenario, the data exclude $\tan\beta > 1.0$ for $m_A$ = 0.25 TeV and
$\tan\beta > 42$ for $m_A$ = 1.5 TeV at the 95% confidence level. For the
Sequential Standard Model, $Z^{\prime}_\mathrm{SSM}$ with $m_{Z^{\prime}} <
2.42$ TeV is excluded at 95% confidence level, while $Z^{\prime}_\mathrm{NU}$
with $m_{Z^{\prime}} < 2.25$ TeV is excluded for the non-universal $G(221)$
model that exhibits enhanced couplings to third-generation fermions.
