Complex sentence: The ships of the green fleet have no velocity relative to each other, so for the clocks on board the individual ships the same amount of time elapses relative to each other, and they can set up a procedure to maintain a synchronized standard fleet time.
Split into simpler sentences: The ships of the green fleet have no velocity relative to each other, so for the clocks on board the individual ships, the same amount of time elapses relative to each other. Therefore, they can set up a procedure to maintain a synchronized standard fleet time.