  We prove the Extended Delta Conjecture of Haglund, Remmel, and Wilson, a
combinatorial formula for $\Delta _{h_l}\Delta' _{e_k} e_{n}$, where $\Delta'
_{e_k}$ and $\Delta_{h_l}$ are Macdonald eigenoperators and $e_n$ is an
elementary symmetric function. We actually prove a stronger identity of
infinite series of $GL_m$ characters expressed in terms of LLT series. This is
achieved through new results in the theory of the Schiffmann algebra and its
action on the algebra of symmetric functions.
