No lamb listed in the ingredients. How much lamb?

Ok, looks like no proofreading or accidental omission.
When that happens, I search for other similar recipes, compare ingredient lists and adapt.
This recipe wants to fill 4-6 zucchini...and I know others that fill 4 or 8 zucchini using about 1/2 lb or 250g ground lamb.
So use that weight as a guideline, then use more or less depending on how much you like lamb and want to highlight it in this dish.