My ZD326 workshop manual does not discuss the fuel line routing at all. Last year I wanted to add a more convenient cartridge fuel filter that filtered both tanks. I had a real hard time figuring out the fuel lines, and decided (probably incorrectly) that the original canister filters were actually in series. My assessment was likely wrong, as it makes more sense that there is one filter servicing each tank.
Anyway, sorry I can't be of more help, other than to confirm that the workshop manual will not be of any use.