Hiya..
Coincidentally, I have both cars like you do, albeit different year models. And am getting exactly the same mileage as you are getting.
Mind you, we cant really compare the truck's mileage to the corolla cos of tyres, aerodynamics, and the different gears (zuki having higher gears naturally).
I initially was also having lower mileage when I first got the suzuki, but change of fluids, air filter, spark plugs.. and also some bottles of fuel system cleaner and carburetor cleaner helps too.
Am thinking of looking into changing out the PCV and oxygen sensor when I can find the parts...
Hope this helps....