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}