documentclass{article}
title{MWE}
RequirePackage[user,savepos]{zref}
begin{document}
Some textpar
clearpage
More textpar
clearpage
On this page, I want to store the vertical position of the following zref. But I want the number to be available as a stored variable, which I can later access, do calculations, and write to the log file (not aux file).par
zsaveposy{here}This is where I want the vertical position. I do not need to take immediate action.par
Yet more textpar
clearpage
And finally, more text.par
end{document}

% In Preamble:
newcommandgetzposy[1]{% zlabel
% Here, it retrieves the number corresponding to the given label
}
% In document body:
Some text.par
zsaveposy{mylabel}And text.par
More text.par
% At the end:
typeout{The y-position of mylabel is getzposy{mylabel}.}