What is the production code for the episode written by Drew Z. Greenberg?
CREATE TABLE table_72723 (
    "Episode No." real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text
)
SELECT "Production code" FROM table_72723 WHERE "Written by" = 'Drew Z. Greenberg'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the production code for the episode written by Drew Z. Greenberg? ### Input: CREATE TABLE table_72723 (
    "Episode No." real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text
) ### Response: SELECT "Production code" FROM table_72723 WHERE "Written by" = 'Drew Z. Greenberg'