I got it.
Turns out that it requires \\
to escape the colon.
$.get(xmlPath, {}, function(xml) {
$("rs\\:data", xml).find("z\\:row").each(function(i) {
alert("found zrow");
});
}, "xml");
As Rich pointed out:
The better solution does not require escaping and works on all “modern” browsers:
.find("[nodeName=z:row]")