Except it is not a true elimination semi-final in that New Zealand has a slight tie-breaker advantage going into this due to a superior (less bad) net Run Rate going into the fixture.
Let’s say 180 is a par score at Seddon Park.
If England bats first
New Zealand would need to lose by fewer than 19 runs and they qualify.
If New Zealand bats first
England would need to chase down the runs with two overs to spare and they would qualify.
The more runs scored and the margin of England’s victory targets decreases slightly, but not by a lot.
If it rains, New Zealand progresses.