Align itemize in multicol with fraction in displaymode

I'm doing a cheat sheet to try to practice with LaTeX. My problem is that after I use itemize + multicols, it shows as below, must be due to that the fraction is in displaystyle. I want the bullet in the middle to be aligned with the other two on the first line. Can anyone show me how to do it?

\documentclass[a4paper]{article}
\usepackage[a4paper,
left=2cm,right=2cm,
top=2cm,bottom=1.5cm]{geometry}
\usepackage{amsmath,amssymb,amsthm}
%\usepackage[utf8]{vietnam}
\usepackage{enumitem}
\usepackage{xcolor}
\usepackage{tcolorbox}
\usepackage{tabularx}
\usepackage{tikz}
\usepackage{multicol}
\begin{multicols}{3}
\begin{itemize}[itemsep = 5pt]
\item $\bar{\bar{z}}=z$
\item $\overline{z_1\pm\overline{z_2}}=\overline{z_1}\pm \overline{z_2}$
\item $\overline{\displaystyle\left(\frac{z_1}{z_2}\right)}=\displaystyle\frac{\overline{z_1}}{\overline{z_2}}$
\item $\overline{z_1\cdot z_2}=\overline{z_1}\cdot\overline{z_2}$
\item $z\bar{z}=|z|^2=a^2+b^2$
\item
\end{itemize}
\end{multicols}
\end{document}

• please always provide a test document that allows people to test answers. arguably you should be using textstyle not displaystyle (as the whole point of textstyle is to avoid altering line space) otherwise increase baseline spacing enough so that you have space for the displayed fractions. May 5, 2020 at 11:13
• Welcome to TeX SX! You should take a look at the tasks package, which is done for this style of layout, without multicols. May 5, 2020 at 11:16
• @Bernard I searched for tasks package. But I couldn't find how to set the bullet symbol. @Carlisle can you help me with the command for doing that. I'm edited my post btw. May 5, 2020 at 11:39
• You could also use a tabular with @{\makebox[2\tabcolsep]{\textbullet}l .... May 5, 2020 at 13:33

Here is a code with tasks. I took the liberty to simplify a bit your preamble:

\documentclass[a4paper]{article}
\usepackage[a4paper, margin=2cm,bottom=1.5cm]{geometry}
\usepackage{amsmath,amssymb,amsthm}
%\usepackage[utf8]{vietnam}
\usepackage{enumitem}
\usepackage{xcolor}
\usepackage{tcolorbox}
\usepackage{tabularx}
\usepackage{tikz}
\usepackage{multicol}

\begin{document}

\task $\bar{\bar{z}}=z$
\task $\overline{z_1\pm\overline{z_2}}=\overline{z_1}\pm \overline{z_2}$
\task $\overline{\Bigl(\dfrac{z_1}{z_2}\Bigr)}=\dfrac{\overline{z_1}}{\overline{z_2}}$
\task $\overline{z_1\cdot z_2}=\overline{z_1}\cdot\overline{z_2}$
\task $z\bar{z}=|z|^2=a^2+b^2$

\end{document}


Just for fun:

\documentclass[a4paper]{article}
\usepackage[showframe,
left=2cm,right=2cm,
top=2cm,bottom=1.5cm]{geometry}
\usepackage{amsmath,amssymb,amsthm}
%\usepackage[utf8]{vietnam}
%\usepackage{enumitem}
%usepackage{xcolor}
%\usepackage{tcolorbox}
%\usepackage{tabularx}
%\usepackage{tikz}
%\usepackage{multicol}

\newlength{\cellwidth}
\newcommand{\fakeitem}[1]{% text as argument
\hskip 0pt plus 0.001fil\allowbreak
\makebox[\dimexpr \leftmargini-\labelsep][r]{\textbullet}%\nobreak
\hskip\labelsep%\nobreak
\makebox[\cellwidth][l]{#1}\ignorespaces}

\begin{document}
\medskip\noindent
\setlength{\cellwidth}{\dimexpr \textwidth/3-\leftmargini}% 3 columns
\fakeitem{$\bar{\bar{z}}=z$}
\fakeitem{$\overline{z_1\pm\overline{z_2}}=\overline{z_1}\pm \overline{z_2}$}
\fakeitem{$\overline{\displaystyle\left(\frac{z_1}{z_2}\right)}=\displaystyle\frac{\overline{z_1}}{\overline{z_2}}$}
\fakeitem{$\overline{z_1\cdot z_2}=\overline{z_1}\cdot\overline{z_2}$}
\fakeitem{$z\bar{z}=|z|^2=a^2+b^2$}
\par\medskip
\noindent next line of text
\end{document}