``<some math>''

enquote{<some math>}

documentclass[preview]{standalone}
usepackage{csquotes}
begin{document}
In text mode:\
Quote by hand: ``Blub''\
Quote by enquote: enquote{Blub}

In math mode:\
Quote by hand: $``a^2+b^2=c^2''$\
Quote by enquote: $enquote{a^2+b^2=c^2}$
end{document}

documentclass[preview]{standalone}
usepackage{csquotes}
begin{document}
In text mode:\
Quote by hand: ``Blub''\
Quote by enquote: enquote{Blub}

In math mode:\
%Quote by hand: $``a^2+b^2=c^2''$\
Quote by hand: ``$a^2+b^2=c^2$''\

%Quote by enquote: $enquote{a^2+b^2=c^2}$
Quote by enquote: enquote{$a^2+b^2=c^2$}
end{document}