Separately grate onion, zucchini and then potatoes in a food processor and transfer to a large bowl.

Pick up small amounts of zucchini-potato mixture by the handful and squeeze out as much moisture as possible.

Reserve all liquid and allow it to settle in a bowl for a few minutes, then carefully pour off the watery part but retain the thick starchy sediment at the bottom of the bowl. Stir thick liquid into potato mixture.

In a small bowl whisk together eggs, oil, salt and pepper and combine with potato mixture.

Add matzo meal to batter, starting with 1/2 cup and adding more if necessary until potato mixture has enough body to form pancakes.

Heat a 1/2-inch depth of oil in a heavy skillet, preferably cast iron.

Form potato mixture into pancakes of approximately 3 inches in diameter and carefully place into oil, taking care not to crowd pancakes.

Fry, turning once, until golden on both sides, for a total of about 6 minutes.

Drain on clean paper bags. Keep pancakes warm while the rest are frying by placing cooked, drained pancakes in a 200°F oven.