How to make the following format

This uses the tabto package, wrapped into a macro \indentitem, with a settable parameter \myindent.

As MadyYuvi notes, any line break in the right-hand bullets will not align with the right column, but reset to the left. I did this because I had the impression that, in such cases, the OP would choose to set the item as a single line, in essence, only using the itemize split for short items.

\documentclass{article}
\usepackage{tabto,enumitem}
\newcommand\myindent{1.5in}
\newcommand\indentitem{\tabto{\myindent}$\bullet$\hspace{\labelsep}}
\begin{document}
\footnotesize
\begin{itemize}[itemsep=0pt, parsep=0pt]
\item zero operation 
\indentitem 3x3 separable conv, repeat 2 
\item skip connection 
\indentitem 3x3 max pooling 
\item 3x3 conv 
\indentitem 3x3 conv, repeat 2 
\item 3x3 separable conv 
\item 3x3 dilated separable conv, dilation=2 
\item 3x3 dilated separable conv, dilation=4 
\item 3x3 dilated separable conv, dilation=2, repeat 2 
\end{itemize} 
\end{document}

With the help of hlist package, can meet the expectation:

\documentclass{book}
\usepackage{hlist}
\begin{document}


\hlist[label={\textbullet}]2
\hitem zero operation
\hitem skip connection
\hitem 3x3 max pooling
\hitem 3x3 conv
\hitem 3x3 conv, repeat 2
\hitem 3x3 separable conv
\hitem 3x3 separable conv, repeat 2
\hitem(2) 3x3 dilated separable conv, dilation=2
\hitem(2) 3x3 dilated separable conv, dilation=4
\hitem(2) 3x3 dilated separable conv, dilation=2, repeat 2
\endhlist


\end{document}

Output:

Two other solutions: with the tasks package, and another the shortlst package. The latter is not part of any distribution, for licensing reasons. Based on it, I defined a tabitemize environment, using two keys: nc for the number of columns 'defaults to 3), and il for the interlining (defaults to 1.5).

For longer items, that must spread through columns, you can use \task* in the place of \task with the first package. Spreading is automatic with the second package.

\documentclass{article}

\usepackage{tasks}
\usepackage{shortlst, xkeyval, setspace}

\settasks{before-skip =\smallskipamount}

\makeatletter
\newcounter{ncol}
\define@key{lex}{nc}[3]{\setcounter{ncol}{#1}}%% 3 columns by default
\define@key{lex}{il}[1.5]{\def\@intln{#1}}% interlining![1]
\newenvironment{tabitemize}[1][]{%
\setkeys{lex}{nc,il,#1}
\settowidth{\labelwidth}{\mbox{\textbullet)}}
\setlength{\leftmargini}{2em}%\setlength{\itemsep}{0pt}
\setlength{\shortitemwidth}{\dimexpr\linewidth/\value{ncol}-\labelwidth-2\labelsep\relax}%
\setstretch{\@intln}
\begin{shortitemize}}%
{\end{shortitemize}
 }%

\begin{document}

\begin{tasks}[style=itemize, after-item-skip=-1ex](2)
\task zero operation
\task skip connection
\task $3×3$ max pooling
\task $3×3$ conv
\task $3×3$ conv, repeat 2
\task $3×3$ separable conv
\task* $3×3$ separable conv, repeat 2
\task* $3×3$ dilated separable conv, dilation=2
\task* $3×3$ dilated separable conv, dilation=4
\task* $3×3$ dilated separable conv, dilation=2, repeat 2
    \end{tasks}

\vspace{1cm}
  \begin{tabitemize}[nc=2, il=1]
\item zero operation
\item skip connection
\item $3×3$ max pooling
\item $3×3$ conv
\item $3×3$ conv, repeat 2
\item $3×3$ separable conv
\item $3×3$ separable conv, repeat 2
\item $3×3$ dilated separable conv, dilation=2
\item $3×3$ dilated separable conv, dilation=4
\item $3×3$ dilated separable conv, dilation=2, repeat 2
\end{tabitemize}

\end{document}