Preheat oven to 170°C. Grate the zucchini coarsely, then toss with 150g caster sugar and set aside for 10 minutes. Squeeze well to remove excess moisture.
Whisk the eggs and remaining sugar in a bowl for 5 minutes, until very light, then fold in the oil, vanilla almond essence and kefir. Mix in the tahini and flour until smooth, then fold in the zucchini.
Spoon into two lined medium loaf pans and bake for 45-50 minutes, until a skewer can be inserted and removed cleanly. Cool on a wire rack.