Our only task is to win the trick containing GREEN 5. With two tricks left and only GREEN 5 and GREEN 6 in hand, the safest cooperative line is to lead GREEN 5 now. Known greens out: 1,2,3,8,9; unknown: 4 and 7. If we lead GREEN 6, the holder of GREEN 7 may be forced to win the trick, taking the lead into the final trick and making it very hard or impossible for us to win GREEN 5. If instead we lead GREEN 5, any teammate holding higher greens can and should duck (play GREEN 4 if they have it, or any off-suit without trump) so we win the task immediately. The only failure case is if someone’s only green is the 7 (or they trump with ROCKET 3), which would likely cause failure regardless if we led GREEN 6. Therefore, lead GREEN 5 to complete the task now while we have control.