Winger Jun Endo added the fourth in the 71st minute and substitute Riko Ueki got the fifth from a penalty in stoppage time after Zambia goalkeeper Catherine Musonda had been dismissed for two yellow cards.
Champions at the 2011 World Cup and runners-up in 2015, Japan lined up in an attacking 3-5-1 formation and looked like a team on a mission from the start.
They had already drawn two fines saves from Musonda, hit the post, and had a Tanaka goal ruled out before Miyazawa struck for the first time in the 43rd minute.
Tanaka had another goal chalked off for offside in the 49th minute and VAR also called back a penalty awarded to Japan a couple of minutes later.
Thai-born striker Tanaka finally got a goal that counted in the 55th minute, sliding Endo’s cross from the left into the right corner of the net.
Tanaka also got the assist on Miyazawa’s second goal in the 62nd minute, pulling the ball back from the byline to allow her teammate the simplest of finishes.
The Nadeshiko were finding space behind the Zambian defence almost at will in the last 20 minutes and a Hasegawa pass found Endo all on her own with only Musonda to beat for the fourth goal 19 minutes from time.
Ueki needed two attempts to convert the late penalty that saw Musonda sent off, substitute goalkeeper Eunice Sakala saving the first but penalised for encroachment.
Zambia captain Barbra Banda, who scored the winner when they beat twice World Cup winners Germany two weeks ago, struck an isolated figure up front and the Africans did not register a single shot at goal.