Aslamualaikum... We are thinking of Amreen Kulsum and Mahreen Kulsum for my twin daughters. Are the meanings of Mahreen and Amreen good and acceptable? What about Zohra and Zaida?

Amreen is an acceptable name. You can read more about it here: Meaning of the names Amreen, Azra, Ayaat and Amani

Mahreen, pronounced [(MU)st + (H)ot] + [p(R)ay + sw(EE)t + (N)ew],  is a variant of Mehreen, pronounced [(ME)t + (H)ot] + [p(R)ay + sw(EE)t + (N)ew]. It is formed from Mehr (friendship, love, compassion, the sun) and -een (like, full of). The full meaning is "full of love", "loving", "compassionate", "brilliant like the sun". It is not an Islamic name but Muslims can use it since it has a good meaning.

For Zohra and Zaida please see: Zohra | Zaida