zm_Fidlers-Green_b2, m_bridge_run_v1, zm_onadega_v3nn, zm_gorodok_v1, zm_tower_of_resistance_v4 and zm_tzuwaza_b5 are all pretty fun ZM maps.

For ZE maps, ze_zombierig_v4_3, ze_biohazard2_sewer_v4c, ze_destruction_of_exorath_v8 and ze_prototype_v2 (I think there's a newer version of this one) are fun but hard maps and might be good for weekend ZE events with the other tryhard maps. ze_licciana_escape_v2 and ze_paradise_v1 are classics and easy enough to just leave in the regular rotation. There's a newer version of ze_trainescape_b3 (http://css.gamebanana.com/maps/97189) that makes it a lot more enjoyable. I'd like to see it updated to that version rather than removed completely.