Preheat oven to 200°C.
Cut potatoes to wedges (baby potatoes — into halves or quarters), drizzle with olive oil, sprinkle with potato spice blend and a pinch of salt, then put to the oven for 15 minutes.
2. Prepare ingredients
Slice one-third of zucchini into thin half-moons.
Cut tomato thinly, accordingly in shape to zucchini.
Remaining zucchini cut into sticks.
3. Prepare chicken
Cut chicken breast crosswise, 3/4 to the bottom but not all the way through, cuts about 0.5–1 cm apart.
Season all over with salt and pepper, then rub with oil.
Tuck tomato and zucchini pieces into cuts, 2–3 in each, alternating vegetables any way you like until you use them all.
4. Put in the oven
Place zucchini sticks next to potatoes on baking sheet, drizzle with olive oil.
Add chicken breast to same sheet, if there’s still room, or use a separate baking dish.
Gently flip potatoes.
Return everything to oven for another 25 minutes.
5. Finish
Take out the sheet pan carefully.
Switch oven to top heat, grill or broil, sprinkle zucchini with grana padano cheese and return to oven for another 5 minutes.
6. Serve
Divide potatoes and zucchini among plates, add chicken on the side.