CREATE TABLE table_72723 ("Episode No." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT)

What is the production code for the episode written by Drew Z. Greenberg?
SELECT "Production code" FROM table_72723 WHERE "Written by" = 'Drew Z. Greenberg'
SELECT "Production code" FROM "table_72723" WHERE "Written by" = 'Drew Z. Greenberg'