1)
What is the meaning of "Kasu Harim Tzilah"?
1.
Radak: This is like b'Tzilah (mountains were covered with the vine's shade). Also "ha'Nimtza Veis Hashem" (Melachim II, 12:11, is like b'Veis Hashem).
2)
What is the meaning of "Anafeha Arzei Kel"?
1.
Rashi: Its branches are like Arzei Kel, i.e. strong cedars, i.e. mighty kings.
2.
Radak: Arzei Kel are very tall. The same applies to "k'Harerei Kel" (36:7). To aggrandize a matter, it is put Samuch to Kel. The same applies to "Ir Gedolah lEi'lokim" (Yonah 3:3).