CREATE TABLE table_14318 ("Outcome" CLOB, "Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Partnering" CLOB, "Opponents" CLOB, "Score" CLOB)

Who was the opponent on clay surface when partnered with Horacio Zeballos?
SELECT "Opponents" FROM table_14318 WHERE "Surface" = 'clay' AND "Partnering" = 'horacio zeballos'
SELECT "Opponents" FROM "table_14318" WHERE "Partnering" = 'horacio zeballos' AND "Surface" = 'clay'