Cut zucchini into rings approx. 0.6 inch (1.5cm) thick. Cut Mozzarella cheese into cubes approx. 0.6 inch (1.5 cm) thick.
Heat olive oil in a small pot and grill the zucchini on middle heat until golden-brown on both sides.
Add water in the pot. Remove the pot from heat after boiling. Add miso and stir it to be completely dissolved. Reheat the miso soup until it is just hot. Never boil the soup.
Add Mozzarella cheese and serve the soup in a bowl immediately because the cheese sticks to the bottom of the pot with time.