As an owner of a z3100 and a z3200 I can verify that the two printers use the exact same ink carts with the exception of red: HP70 (HP73 for the chromatic red on a z3200).
Parts List.
HP z3200 ink price per mL: $.50 (used to be $.38 when twin packs were available)
Canon 8400 price per mL (700 ml size): $.42