WELLINGTON (Reuters) - New Zealand Green Party leader James Shaw said on Saturday he would be willing to work with Labour Party to form a government with the populist New Zealand First Party as counting showed the ruling National Party on track to secure the most votes but fall short of an outright majority.   Shaw said his message for New Zealand First Party leader Winston Peters was that now was the time to put differences aside and work with Labour to overthrow the incumbent Nationals.     His comments came after 93.7 percent of the results counted showed Labour on 35.7 percent of the vote and center-right National on 46.2 percent. Those results suggested either major party would need New Zealand First to form the next government. The Greens have a working agreement with Labour. The final tally of all votes would not be released until Oct. 7. 