as transient as a fleeting cloud (/drifting clouds); ephemeral ❍ 论起荣华富贵，原不过是“～”；……(《红楼梦》1513) Of course wealth and honour are transient as drifting clouds.
过眼云烟
as transient as a fleeting cloud;like a puff of smoke;ephemeral 一切荣华富贵都是～。All fame and wealth are just a flash in the pan.
过眼云烟烟云过眼ɡuò yǎn yún yān
在眼前飘过的云烟，一去不复返。比喻很快就消失的东西。as transient as a fleeting cloud, ephemeral, pass from one’s view