Boil the zucchinis until tender (approximately 8-10 minutes).

Let the zucchinis cool slightly.

Cut the cooled zucchinis in half lengthwise.

Scoop out the insides of the zucchini halves.

Place the scooped-out zucchini pulp in a strainer and press out as much liquid as possible.

In a bowl, combine the zucchini pulp, finely chopped hard-boiled egg, grated cheese, and milk.

Mix the ingredients thoroughly.

Fill the zucchini shells with the mixture.

Sprinkle the filled zucchini shells with breadcrumbs and grated Parmesan cheese.

Preheat oven to 350F (175C).

Bake in the preheated oven for approximately 10-15 minutes, or until the Parmesan cheese is browned and the filling is heated through.

Let cool for 5 minutes before serving.