I have found some satisfying start of answer to my problem on this related post`
Sadly with the code displayed hereunder, the equation number is displayed on the same level as the last equation line (on picture here even lower because the line is so long). Can anyone tell me how to set the height of the equation number to be the same as the second line?

\documentclass[11pt, a4paper, twocolumn]{article}
%\input{structure.tex}
\usepackage{bm}
\usepackage{graphicx}
\usepackage{etoolbox}
\usepackage{float}
\usepackage[english]{babel} % English language hyphenation
\usepackage{amsmath,amsfonts,amsthm}
\begin{document}
\begin{equation}\label{eq:DCKE}
\begin{aligned}
\frac{\delta}{\delta t}&p(\textbf{z},t) = -\sum_i{\frac{\delta}{\delta z_i} [A_i(\textbf{z},t)p(\textbf{z},t)]}\\
& +\sum_{ij}{\frac{1}{2}\frac{\delta ^2}{\delta z_i\delta z_j}[B_{ij}(\textbf{z},t)p(\textbf{z},t)]}\\
& +\int{}d\textbf{y}[W(\textbf{z}\mid\textbf{y},t)p(\textbf{z},t)-W(\textbf{y}\mid \textbf{z},t)p(\textbf{z},t)]
\end{aligned}
\end{equation}
\end{document}]

twocolumnoption from your class, it works as supposedly expected – BambOo Sep 10 '18 at 17:34