PORTLAND — Zach Collins had 13 points and No. 3 Gonzaga remained the nation’s only undefeated Division I team with an 83-64 victory over Portland in a game Monday night that was rescheduled because of a winter storm earlier this month. The Bulldogs have won 20 straight games, their longest streak since winning that many in the 2005-06 and 2003-04 seasons.