Combine biga and water in a large bowl and whisk to combine. Mix in flours, salt and pepper, blending by hand to mix in the flour. Cover with a damp cloth and let rest 30 minutes to an hour.
Knead in the zucchini and cheese. A bit more flour may be needed if dough seems too wet.
Cover dough with a damp cloth and let rise at room temperature until doubled, about 8-10 hours.
Remove the dough to a floured surface. Shape it into a round, flip it over and let rest for 5-10 minutes. Line a bowl or proofing basket with a cloth and dust with flour. Tighten the dough and place it seam side up in the proofing basket. Cover the dough and let rise until puffy, about 30 minutes to an hour. Preheat oven to 450 degrees.
Cut a sheet of parchment paper and place it over the dough, then invert the bowl to release the dough. Sprinkle Roth flour and rub in gently. Score the bread, transfer it into a Dutch oven and put on the lid.
Bake for 20 minutes then remove the lid. Bake another 25 minutes, then remove bread from pot and bake the last 10 minutes on the rack.
Cool on a wire rack and try to wait an hour before slicing the loaf.