<human>: Can you succinctly summarize the text in 1-3 sentences?

My boyfriend and I are going to be moving into a new apartment this weekend and within the week will be bringing our cats. We have two cats, one who is a year and a half that we've had since he was 6 weeks old and a 7 year old female cat we adopted from a shelter back in March. When we brought home the female cat from the shelter we kept her in a separate room for two weeks and tried to slowly introduce them to one another. However the younger cat being exceptionally curious and playful would find ways to sneak into the room when we weren't looking to inspect the new comer.

We thought the female cat would be okay with the him, she had been in a large play area with 5 other cats from the shelter when we adopted her. It didn't go well with those two. The younger cat constantly batted at her tail wanting to play and she would hiss at him, but never really swat at him (initially).

However the female cat began puking EVERY day, she sheds a lot so initially we thought it was just hairballs but once it became daily we took her to the vet who found nothing wrong with her. Both my boyfriend and I think it's from stress having the male cat antagonize her. 

Anyway at our old place we got a massive flea infestation (don't know how, both of our cats are strictly indoors) and one cat went to my parents house another went to his parents house. The flea thing cleared up, both of us had to move back in with our parents for a bit before we found a new place.

The cats have been separated for 4 months now and we'll be bringing them to our new apartment within the week. Any advice as to how to reintroduce them so this might not go so hellishly this time? I couldn't give up either one of them.
<bot>: Two cats hated each other, been separated 4 months and need advice on how to reintroduce them so they can at least tolerate one another.