who is the the incumbent with candidates being jack z. anderson (r) unopposed
CREATE TABLE "table1_1342233_6" (
  "district" text,
  "incumbent" text,
  "party" text,
  "first_elected" real,
  "result" text,
  "candidates" text
);
SELECT "incumbent" FROM "table1_1342233_6" WHERE "candidates"='Jack Z. Anderson (R) Unopposed';