TMK, the only transpac route that CZ flies is CAN-LAX, not very optimal for a train ride that ends in BJ or SH. Furthermore, while their seat pitch isn't horrible, CZ is one of the few airlines I know of that manages to cram 10-abreast into a 777. Bad food and dreadful customer service are two other themes that come to mind.

Basically, of all the airlines connecting the US and China (CA, AC, MU, AA, UA, CO, NW, DL, JL, NH, OZ, KE, CI, CX, HU...), CZ is at the bottom of my list. Pricewise, things are pretty competitive right now so you should have lots of options from which to chose. The past several one ways I've purchased have been on MU, CA, UA, NW, and OZ. In each case, I paid around $700 (not much more than half the cost of a round trip).