Teresa Abelleira opened the scoring in the ninth minute before Hermoso and Redondo converted their respective braces for Spain.
Hermoso scored in the 13th and 70th minutes, and Redondo tallied in the 69th and 85th minutes.
Misa Rodriguez made two saves for Spain, who will battle Japan, also with two wins, on Monday for the top spot in Group C.
Eunice Sakala finished with eight saves for Zambia, who will clash with Costa Rica on Monday for third place.
Japan 2, Costa Rica 0
Hikaru Naomoto scored in the 25th minute and Aoba Fujino tallied two minutes later to help Japan punch its ticket to the knockout round in Dunedin.
Naomoto took advantage of a slip from Maria Paula Coto and unleashed a shot that sailed past goalkeeper Daniela Solera.
Fujino converted from a sharp angle just two minutes later for Japan.
Ayaka Yamashita made two saves for Japan, while Solera finished with 10 stops for Costa Rica.
Canada 2, Ireland 1
Adriana Leon scored in the go-ahead goal between two defenders in the 53rd minute to lift the Canadians to victory in a Group B clash in Perth.
Canada, with one win and one draw, also benefited from an own goal in first-half stoppage time to forge a 1-1 tie after Katie McCabe scored off a corner kick in the fourth minute for Ireland, who now have two defeats.
Kailen Sheridan made five saves for Canada, while Courtney Brosnan finished with six stops for Ireland.
Canada returns to action against Australia on Monday in Melbourne. Ireland, in turn, will tangle with Nigeria on Monday in Brisbane.