Cut the zucchini into vertical strips 1 cm thick.
Peel potato and cut it into strips of the same thickness.
Line a dripping pan with edible paper, place there zucchini and potato, dredge the half of thyme leaves, salt, pepper, and drizzle some olive oil.
Grill the vegetables and fry them until golden brown from each side.
Salt and pepper the tuna. Zest the lemon with a fine grater, dredge the fish with the zest and grease the fish all around with olive oil.
Take the baked zucchini out of the oven, and instead of it put the fish onto the dripping pan with potato, grill until done.
Put zucchini strips onto the plate, then add potato and fish, pour with the juice obtained during baking.
Squeeze some juice from the lemon, drizzle it onto the fish with vegetables, dredge the remaining thyme.