Why does it say "Chaze Tziyon"?
Rashi: Who should you see in your heart to consider kingship and authority? Tziyon, which was the city of our meeting place.
Radak: You will not see "Am No'az" (19). Rather, you will see Tziyon.
Malbim: You will see that Tziyon will be Kiryas Mo'adenu.
Why is it called "Kiryas Mo'adenu"?
Radak, Malbim: They came there three times a year, on the Mo'adim. It was not Kiryas Mo'adenu in the days of Malchei Yisrael, for all of Yisrael did not come (Malchei Yisrael established guards to stop people from coming). Also in the days of Achaz 1 , Mo'adei Hashem and His Korbanos were Batel. Also at the beginning of Chizkiyah's kingship, he wrote letters to Efrayim and Menasheh that they should come to Yerushalayim to do Pesach, and they mocked the messengers.
Even though the 10 tribes were exiled in the days of Chizkiyah, the last Melech Yisrael, Hoshe'a ben Elah, abolished the guards. Had Achaz been a Tzadik, they could have come. (PF)
Why does it say "your eyes will see Yerushalayim Naveh Sha'anan"?
Radak: Until now, it was not a serene place. The hand of Nochri kings was over it.
Malbim: Even though you cannot depict Yerushalayim as the city of an awesome king who has great camps and fortified cities, you can depict it nicer - a serene pasture.
What is the meaning of "[Ohel] Bal Yitz'an"?
Rashi: It will not bow 1 . This is like "Elon b'Tza'ananim" (Shoftim 4:11); the Targum is Meishar Agnaya, i.e. clefts in the field, like 'Agnei 2 d'Ar'a Mikri.' Water gathers there from the mountains and mounds. The Beis in b'Tza'ananim is a prefix; it is not part of the word itself.
Radak citing Targum Yonasan: Like a security that will not be redeemed. We do not find like this anywhere in Tanach.
Radak citing his father: The root is Yatza. The Nun is added, like Binyan, Kinyan, Alman, Rachaman. The tent will never descend and be spread [on the ground]; it will always be pitched.
Malbim: In the pasture is the tent of the shepherd, Chizkiyah. He will never be expelled - if he goes in Hashem's ways, and his heart is complete with his G-d.
What is the meaning of "Bal Yisa Yesodosav"?
Rashi: The pegs to which they tie the ropes of the Ohel, they will not be moved 1 from the ground, in which they are inserted. This is like "va'Yasi'u Avanim Gedolos" (Melachim I, 5:31), "va'Yisa'em Im ha'Beri'ach" (Shoftim 16:3), uprooting.
Radak: Even one of them will not be moved. (Therefore, it says Yisa (singular). - PF)
Will they never be moved?
Radak: "La'Netzach" means for a long time.