Dog territorial behaviour

Question
Hello. My parents have 4 dogs (3 cocker spaniels and 1 shiba inu). They got them at different times and have never really trained them to be around each other. The shiba inu is very territorial and did not like the cockers when they were puppies so they have been separated for years. He does get along with 1 of the cockers though. They are always separated in pairs at opposite ends of the house. My question is what can we do to un-separate these dogs? My parents crate them at night so they do not attack each other but I think that with a little work they could all get along and we could have them out together at the same time. Should I just put them all together and let them work it out on their own? My mother is afraid that they will attack each other and get hurt. Thanks so much for your help!

Answer
The best thing to sort out this problem,would be to muzzle them-then they can sort out there pack order,but no one can get hurt I have done this on a large number of dogs and it works well

While in a lot of cases they won't be best friends,they will at least tolerate each other without constant fighting or worries about anyone getting hurt