What is the meaning of "v'Nikeisi Damam Lo Nikeisi"?
Rashi: Even if I will cleanse them from other sins and evils that they did to Me, I will not cleanse them from the blood of Bnei Yehudah.
Radak: I will cleanse them from their silver and gold that they took. Also Yisrael will take from them in the future, and they will be plundered. I will not cleanse them from the blood that they spilled, rather, [they will pay] Nefesh Tachas Nefesh - I will take the life of the murderers or their children. All the silver and gold in the world that they will give to atone for their souls, they will not be clean from the blood that they spilled.
Radak, according to Targum Yonasan: "Damam" is connected to v'Nikeisi. I took payment for their blood from the nations - I will again take payment 1 .
Malbim: The war of Gog and Magog involved only Edom, Yishmael and those who have their Emunah. Many nations do not pertains to them, and also they spilled blood of Yisrael. I will clean (avenge) the blood that I did not clean in the fall of Gog.
It seems that "Lo" means that I did not finish taking payment. (PF)
Why does it say "va'Shem Shochen b'Tziyon"?
Rashi: This will be when Hashem dwells in Tziyon.
Radak: This explains why Yehudah will always dwell - because Hashem will always dwell in Tziyon after it returns in the days of Mashi'ach. And so Yechezkel sealed his Nevu'ah "v'Shem ha'Ir mi'Yom Hashem Shamah" (48:35)
Malbim: After Hashem dwells in Tziyon, He will clean the other blood (refer to 4:21:1:4) and do judgment for it.
