Technically, I believe a female can get pregnant immediately after her last litter. However, I would at the very least want to wait until the babies were at least 8 weeks old when they can start being rehomed. Otherwise you're going to have a rabbit trying to nurse kits of two different ages and the young ones will struggle.
That being said, breeding a rabbit repeatedly like that puts a lot of physical strain on them. Are you sure you can safely rehome another litter so soon?