Existing book lending relationship database: books (book number, title, author, unit price, inventory), readers (reader number, name, work unit, address), lending (book number, reader number, lending period, return period, remarks), in which the return period is empty, indicating that books have not been returned. Answer the following questions according to this set of relationship patterns:

(1) Write the reader's name with the book number "007B" with relational algebraic expression;

(2) Write the title of the book borrowed by the retrieval reader "Zhang San" with relational algebraic expression;

(3) Search the titles of books borrowed by the reader "Zhang San" with SQL statements;

(4) using SQL statement to delete the information of the books borrowed by the reader "Zhang San" from the borrowing table;

(5) Using SQL statement to retrieve the title of the book borrowed by the reader "Zhang San";

(6) Use SQL statement to establish the reader's name and unit view of the unreturned books.