CZ aren't quite a world-class carrier on the standard of CX, KE or SQ, but they're quite decent in my experience. Meals are substantial and decent, IFE is decent. Airport transfer is a bit of a PITA with the possibility of long walks and long waits, but the lounge is excellent with showers, two floors of sitting area (one is a dining room) and a full buffet including cook-to-order soup and noodles. I'd fly with them again without hesitation although my first preference would be for CX on that route!

My favorite element of the CZ in-flight experience is their exercise video shown prior to arrival. It's so Chinese in a charming sort of way.

Edited to add: looks like, depending on the day you fly, the outbound requires a lengthy layover in CAN. I believe that CZ offers its premium class passengers layover accommodations at the nice Pullman hotel near the airport. You can also grab the metro in from the airport straight into CAN for a walk around. Transit time into CAN is about 40-45 minutes on the shiny new train. Note that immigration authorities WILL permit transit without visa entry for up to 24 hours in CAN (provided you are traveling from one of the approved countries). That's provided on arrival in CAN and may require a little explaining. If you've got the hotel booking that will help expedite or affirm your intent to move onward from China

CAN is a nice layover city - you can get in to see a few nice sites, like the Chen Family Temple, right on the subway. 12 hours is plenty for that.