Houston won on the road for the first time in five tries and has been victorious in each of its last six trips to Memphis.
Martin and Lowry both scored 28 points while combining to hit 18-of-28 shots from the field. The Rockets made 59 percent of their field goal attempts, 23-of-26 from the line and 16-of-23 from 3-point range.
Houston pulled away late after leading by only four early in the fourth quarter.
Rudy Gay had 29 points for Memphis and Marc Gasol scored 20. The Grizzlies have lost two in a row and had a four-game home winning streak snapped.