vertical space after (not between) items

Question

I just want to add some vertical space after each item in a list. However, the usual options provided by list customization packages only modify the space between items.

In other words, I want to insert N vertical spaces after N items, not like itemize does, which inserts N-1 vertical spaces between N elements (by increasing the itemsep dimension provided by the enumitem package)

Note. I would like to insert space in a systematic way (see the MWE), since my final goal is to define a new environment that does it.

\documentclass{article}

\begin{document}

\begin{enumerate}
\item First question
\begin{itemize}
\item Solve: $x^2+1=0$
\vspace{2em}
\item Solve: $x^3+1=0$
\vspace{2em}
\item Solve: $x^4+1=0$
\vspace{2em}
\end{itemize}
\item Second question
\end{enumerate}

\end{document}

Answer 1

If I well understood what you want, here is a way:

\documentclass{article}
\usepackage{enumitem}

\begin{document}

\begin{enumerate}
\item First question
\begin{itemize}[itemsep=3em, after=\vspace*{\dimexpr 3em-\topsep-\partopsep}]
\item Solve: $x^2+1=0$
\item Solve: $x^3+1=0$
\item Solve: $x^4+1=0$
\end{itemize}
\item Second question
\end{enumerate}

\end{document}