Quick summary of the combat portion of chapter 25:
Merged Zamasu and MSSJB Goku continue to go toe to toe with each other, then as a last resort, Goku uses the 'destruction' technique on MZ. As Goku is in the middle of destroying MZ, MZ uses a portal opening to grab Mai and put her in front him, which results in Goku terminating his destruction of MZ to prevent Mai from suffering it instead. This gave MZ an opening, which he used to kick Goku away. Trunks then went in for the attack but got blown away when MZ glared at him. Before MZ wipes the planet out, Goku Black and Zamasu partially split, then they attempt to become one again, only to fail when Trunks slices their partial merger in half, causing Black and Zamasu to fall down. Trunks then impales Goku Black with his sword whilst he's still on the ground, thinking that he finished him for good... only for Black to blast him in the back. Black then takes the sword that was dug into him out of his body, then crushes it, and transforms into a replica of Merged Zamasu. Zamasu then turns into a replica of Merged Zamasu too, and they both begin stomping Goku. Vegeta then gets mad and kicks Goku away, then releases his new technique [Gamma Burst Flash] on the two copies of Merged Zamasu, which cause their bodies to divide into small pieces. Soon after, numerous Merged Zamasu's emerge.