Seventh-seeded Akron advances to play No. 3 Kent State in the quarterfinals on Thursday.
Akron hit four consecutive 3-pointers, one apiece from Cheatham, Jackson, McAdams and Jake Kretzer, to take a 45-35 lead with 7:50 left. The Zips were 12 of 29 (41 percent) from 3-point range compared to just 2 of 14 for Western Michigan.
Thomas Wilder had 12 points and seven rebounds for sixth-seeded Western Michigan (20-13), which was held to 14-of-54 shooting (25.9 percent).
Western Michigan trailed by seven at halftime, but held Akron to just one field goal in the first eight minutes of the second to pull even at 30.