You cannot facing the extreme intelligence of WA because non-atomic symbol names seem to become interpreted as a product
which is the conventional meaning, indeed. Just use poor man's solution calling your
$xy$ variable simply
$z$.
P.S.: The habit to interpret
$xx$ as
$x^2$ can be justified by e.g. Newton's handwriting, starting with the third power an exponent was used, the second power was written by repetition of the symbol ...
