Work in concert

• Do together
• Perform as one
• Work together, as organisms
• Do in tandem
• Work in tandem

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Coact \Co*act"\, v. i. [Pref. co- + act, v. i.] To act together; to work in concert; to unite. [Obs.] But if I tell you how these two did coact. --Shak.

WordNet Word definitions in WordNet
v. act together, as of organisms

Wiktionary Word definitions in Wiktionary
Etymology 1 (context obsolete English) forced, constrained, done under compulsion. v (context obsolete English) To compel, constrain, force. Etymology 2 vb. (context rare English) To work together.