documentclass[12pt,a4paper,landscape]{article}
usepackage[utf8]{inputenc}

usepackage{amsmath,bm}
usepackage{amsfonts}
usepackage{multicol}
usepackage{blindtext}

usepackage[left=0.5cm,right=0.5cm,top=0.5cm,bottom=0.5cm]{geometry}


begin{document}
begin{multicols}{3}
blindtext
begin{equation}
The following equation shows ...
mathcal{L}(q)=E_{q(tau)}[log p(tau)]+E_{q(theta)}[log p(theta)]+E_{q(mathbf{z}) q(tau)}[log p(mathbf{z} | tau)]
end{equation}

begin{align}
The following equation shows ...
mathcal{L}(q)=E_{q(tau)}[log p(tau)]+E_{q(theta)}[log p(theta)]+E_{q(mathbf{z}) q(tau)}[log p(mathbf{z} | tau)]
end{align}

blindtext
end{multicols}
end{document}