For the zucchini tzatziki, place grated zucchini in a strainer lined with a clean tea towel, add a pinch of salt and mix salt through using your hands. Leave it sit for 10 minutes.
Meanwhile, chop lamb fillets into bite size pieces and place into a bowl. Add all remaining souvlaki ingredients to the lamb, mix well with your hands, cover and refrigerate to marinate for an hour or overnight.
To finish the zucchini tzatziki, gather the sides of the tea towel and squeeze out all the liquid (you should be left with about half a cup of grated zucchini). Place in a bowl with all remaining tzatziki ingredients, stir to combine, cover and refrigerate until needed.
Thread the lamb onto skewers (I like to use metal skewers so they don’t burn). You can cook the souvlaki on the barbeque, grill or griddle pan. Either way, cook over a med-high heat, turning them occasionally for 4-5 minutes until golden or to your liking.
To serve, place lamb on a platter, squeeze lemon juice all over and serve alongside your zucchini tzatziki.