joint — the place at which two things, or separate parts of one thing, are joined or united, either rigidly or in such a way as to permit motion; juncture.
collaborating — to work, one with another; cooperate, as on a literary work: They collaborated on a novel.
collaborative — A collaborative piece of work is done by two or more people or groups working together.
collusive — Collusive behaviour involves secret or illegal co-operation, especially between countries or organizations.
combined — A combined effort or attack is made by two or more groups of people at the same time.
concurring — to accord in opinion; agree: Do you concur with his statement?
hand in glove — the terminal, prehensile part of the upper limb in humans and other primates, consisting of the wrist, metacarpal area, fingers, and thumb.
participating — to take or have a part or share, as with others; partake; share (usually followed by in): to participate in profits; to participate in a play.
synergic — the interaction of elements that when combined produce a total effect that is greater than the sum of the individual elements, contributions, etc.; synergism.
cooperative — A cooperative is a business or organization run by the people who work for it, or owned by the people who use it. These people share its benefits and profits.
synergistic — pertaining to, characteristic of, or resembling synergy: a synergistic effect.