How do I make a multiline equation but giving this only one equation number

Question

I want all these three equations to be known as (1). Not (1), (2), (3).

\documentclass[11pt]{article}


\usepackage{fancyhdr, lastpage}
\renewcommand{\headrulewidth}{0pt}
\pagestyle{fancy}
\fancyhf{}
\fancyfoot[C]{{\thepage} of \pageref{LastPage}}

\usepackage{amsmath}
\usepackage[T1]{fontenc}
\usepackage{booktabs, caption}
\usepackage{tabularx}
\DeclareMathOperator*{\plim}{plim}
\usepackage{threeparttable}
\usepackage{booktabs}
\usepackage{dcolumn}
\usepackage{pdflscape}
\usepackage{longtable}
\usepackage{threeparttablex}
\usepackage{lipsum}

\begin{document}


\begin{align}
E[y_i |z_i] &= \beta +\alpha E[d_i |z_i] + E[u_i |z_i] \\
 &= \beta+\alpha P(z_i) +E(u_i) \\
 &= E[y_i|P(z_i)] 
\end{align}

\end{document}