Tied at one win each through the first two games, Zalgiris went on to win the final three contests of the season to clinch their sixth consecutive title.
Motum was especially efficient coming off the bench in the last two games, averaging 12.5 points, 3.5 rebounds and 1.5 assists while hitting 10-12 from the field overall.
Fellow Australian Angus Brandt was unable to swing the series in Neptunas' favour despite moving into the starting line-up for Game 4 where he collected six points and six boards.
The Championship caps a memorable debut season in Lithuania for Motum and he will soon head home for training camps with the Australian Boomers as they prepare for Rio and the Farewell Series at Hisense Arena on July 12 and July 14.
Further East in Europe, David Andersen is on the precipice of finishing second in the French national league as his side, ASVEL, has gone down 0-2 in their Finals series against Strasbourg.
Andersen recorded an equal game-high 19 points in the first clash, hitting 7-8 from the free-throw line before tallying six points and four rebounds in Game 2.
Meanwhile in the USA, Andrew Bogut and the Golden State Warriors have stunned Matthew Dellavedova and the Cleveland Cavaliers to go up 2-0 in their series.
Bogut was at his defensive best in Game 2, recording a playoff career-high five blocks in combination with six rebounds, two steals and two points.
Dellavedova showed his trademark grittiness, not giving up the fight as he scored seven points off the bench but the game had been lost long before he saw court time.
The series now shifts to Cleveland for two games but Bogut's side looks well on their way to capping off the most dominant season in NBA history with a second consecutive ring.
Following the culmination of their seasons, Andersen, Bogut and Dellavedova will all join Motum for the Boomers training camp.
Tickets for the Farewell Series can be purchased here.