“There was also another great eagle with great wings and many feathers, and behold this vine bent its roots towards him, and shot forth its branches towards him from the beds of its plantation, that he might water it. It was planted in a good field by many waters that it might bring forth branches, and that it might bear fruit, and that it might be a goodly vine.”
The second great eagle is Egypt (Ezekiel 17:15). It too is mighty but it has no long pinions, nor is it as splendid. But Zedekiah was drawn from his loyalty and transferred his fealty to Egypt under Pharaoh Hophra (Jeremiah 44:30). His aim was that he might be watered by Egypt as he had been by Nebuchadnezzar and grow and be fruitful. Ezekiel 17:8 is almost a repetition of Ezekiel 17:6. What Nebuchadnezzar had done for him he also sought from Egypt, but he hoped it would be in much more freedom and with greater honour as a goodly vine rather than one of low stature. He was anticipating the same prosperity from his alliance with Egypt. But it was a hope and not a reality. And it never came to fruition. (Some see Ezekiel 17:8 as recapping what Nebuchadnezzar had done for him, but the sequence suggests it refers to Egypt).
In both cases the vine is planted in Palestine, but watered first from Babylon and then Egypt. Each is seen as the source of water from their great and famed resources.