I use Driven: Primal Impulse in my Z. I use the vent sticks.
The Driven Scents
It was very different from the sea of floral scents and was distinctive enough that I could easily associate the smell with the Z. My parents aren't big fans, but my friends usually point it out favorably when they sit in the car for the first time.
Never seem the Treefrog air fresheners before. Might have to pick up a pack if I ever see it around.