Peel the zucchini and coarsely grate it into a large bowl.
Squeeze the grated zucchini firmly (a clean kitchen towel works well) and pour off all the released liquid.
Add the bread crumbs and ground flaxseed to the squeezed zucchini, season with salt and pepper, and mix well until everything holds together.
Roll the mixture into walnut-size balls — you should get about 14.
Heat ¼ cup (60 ml) of the olive oil (for frying) in a pan over medium-high heat and fry the zucchini balls for 2–3 minutes, turning them, until golden on all sides.
For the dressing, whisk the balsamic vinegar with ¼ cup (60 ml) of the olive oil (the dressing portion), salt, and pepper.
Place the chopped lettuce leaves in a salad bowl, pour the dressing over them, and toss to coat.
Arrange the warm zucchini balls on top of the dressed lettuce and serve immediately, before the balls cool.
