What are the average points for an engine of ford zetec-r v8?
CREATE TABLE "complete_formula_one_results" (
  "year" real,
  "chassis" text,
  "engine" text,
  "tyres" text,
  "points" real
);
SELECT AVG("points") FROM "complete_formula_one_results" WHERE "engine"='ford zetec-r v8';