KiwiFlyer - AC discontinued Z class as an Economy bucket some time ago. It's recently reappeared, but is now a Discounted Business fare bucket on some routes and a Web Fare Business on others. Their new structure looks like -

J CABIN - J C Z as revenue, I for Aeroplan FF upgrades, D for rewards.
J C Z eliglble to earn COS bonus, but there are different policies for different routings in the internal AE scheme. As such, I strongly suggest a check of host FF schemes information to see if AC will pay a C COS on a route you are interested in, in particular.

Y CABIN - Y M U B H V Q L A R K N G P E T are revenue, W for rewards.
Classes that will need checking via host FF schemes as far as mileage earning potential goes are R K N G P E T, on both international and internal North American routes. Carribbean routes also have different earning policies.

S class seems to have gone as AC has dropped their Club Class product.