level 73 The key is the two blocks on the upper left with the two-way a…

level 73
The key is the two blocks on the upper left with the two-way arrows.
On bottom left, take out three green.
Upper, take out green, yellow, red and white. Let the two is the two blocks on the upper left with the two-way arrows drop down onto the black blocks. Use those arrow blocks to take out the two blocks with X's. The top green will drop down and then it is easy to complete!