Jordan Breen explains the significance for the Japanese MMA scene:
In order to understand the significance of the agreement, one must pay mind to the larger promotional affiliations of each promotion in the past.
ZST, a direct descendent of the Rings Fighting Network, served as a pathway for talent to Hero's under the supervision of Rings founder Akira Maeda (Pictures). This relationship saw the elevation of talents such as Tokoro, Remigijus Morkevicius (Pictures) and Kestutis Smirnovas (Pictures).
Meanwhile Deep acted as a smaller sister promotion to Pride. Saeki, while Deep's president, also served as a public relations officer for Pride and was responsible for much of the native talent competing in the Bushido brand.
Given this history, the relationship between Deep and ZST parallels the rise of Dream, which was founded when Hero's backer Fight Entertainment Group welcomed executives from former Pride parent company Dream Stage Entertainment. Saeki and Uehara both said that they hope the relationship between the two promotions can foster talent and funnel them toward Dream in the future.
Neither promoter was sure how inter-promotional bouts would work in terms of rules. Deep allows for soccer kicks and stomps in some instances while many of ZST's bouts still use traditional Rings rules, with no ground-and-pound to the head. However, both had ideas of fighters who they thought could benefit from the arrangement.
This can only be good for grooming the next generation of Japanese superstar fighters.