TCAS II has specific algorithms to deal with cases where two or more other aircraft are simultaneously considered to be threats – ‘Multi-aircraft logic’.
Because TCAS only issues resolutions advisories in two senses (‘up’ or ‘down’’) the coordination and resolution of multiple threats cannot be ideal.
Generally, one aircraft will be instructed to pass above all the other threats, one aircraft will be instructed to pass below all the other threats, and the other aircraft will be instructed to fly level.