May is shaping up to be a significant month for K-pop boy groups whose origins trace back to survival shows. Three acts are returning within weeks of each other, each navigating a different kind of transition as they look to establish or redefine their place in the market. Leading the charge is ZEROBASEONE, which debuted through Season 1 of Mnet's survival audition show "Boys Planet" and has since reorganized as a five-member group. Originally a nine-member act, the team wrapped up its original formation following a concert at KSPO Dome on March 15, before reconstituting with members Sung Han-bin, Kim Ji-woong, Kim Tae-rae, Matthew Seok and Park Gun-wook. The group will release its sixth mini-album, "Ascend-," on May 18, featuring seven tracks including the title song "TOP 5," B-sides "Intro.," "V for Vision," "Customize," "Exotic," "Changes" and "Zero to Hundred." With six consecutive million-selling albums to its name, the question now is whether the slimmed-down lineup can sustain that momentum. In a notable coincidence, May 26 will see four former ZEROBASEONE members — Zhang Hao,