In this work, we demonstrate the bottom up on-surface synthesis of poly(para-dibenzo[bc,kl]-coronenylene) (PPDBC), a zigzag edge-encased analog of poly(para-phenylene) (PPP), and its lateral fusion into zigzag edge-extended graphene nanoribbons (zeeGNRs). Toward this end, we designed a dihalogenated di(metaxylyl)anthracene monomer displaying strategic methyl groups at the substituted phenyl ring and investigated its applicability as precursor in the thermally induced surface assisted polymerization and cyclodehydrogenation. The structure of the resulting zigzag edge-rich (70%) polymer PPDBC was unambiguously confirmed by scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM). Remarkably, by further thermal treatment at 450 C two and three aligned PPDBC chains can be laterally fused into expanded zeeGNRs, with a ribbon width of nine (N = 9) up to 17 (N = 17) carbon atoms. Moreover, the resulting zeeGNRs exhibit a high ratio of zigzag (67%) vs armchair (25%) edge segments and feature electronic band gaps as low as 0.9 eV according to gaps quasiparticle calculations.