Diagrammatic Mass Factorization

We develop an analogy between mass factorization and multiplicative BPHZ-renornalization with the role of the renormalization constant being taken over by the operator matrix elements. By introducing Zimmernan's forest formula we demonstrate its use in constructing the deep inelastic DI)/Drell-Yan (DY) factorized parton crosssections and arrive at an all-order proof of nass factorization. The DY correction terra is determined by similar reasonings