1)
Why does the Torah need to write both "Z'chor" and "Al Tishkach"?
1.
Sifra (Bechukosai, 27:3): "Al Tishkach" means to remember it in the heart; "Z'chor", to verbalize it. 1
1
See Torah Temimah, note 1, who elaborates.
2)
What is the meaning of "Mamrim"?
1.
Rashi (Erchin, 15a) Targum Onkelos and Targum Yonasan: It means 'rebels'.
2.
Rashi (in Ki Seitzei, 21:18): It means - 'angered'; (in Melachim 2, 14:26) - 'opposed'; (in Yirmiyah, 4:17) -'troublesome; (in Tehilim, 140:1) - 'warmongers'.
3)
Why does the Torah write "Mamrim Heyisem Im Hashem" and not 'ba'Hashem' or 'Lifnei Hashem' (See Oznayim la'Torah)?