What are the challenges in changing a PhD supervisor after 2/3 of PhD is done I am doing good in my Ph.D. but I do not like my supervisors. The following are the reasons:


I am forced to work in a very specific area and there is almost no room for creativity. Any related idea which goes against the "vision" of my supervisor is dealt with fierce questions. If I answer them all, then I am told that until someone else with reputation does it, I should not try it as I do not have a proven track record. I am forced to continue on previous PhDs, which I did and have satisfied. But I wish to explore my ideas too.
My supervisor openly claims that he is a great researcher and expects students to worship him. He has lots of grants and publications, but I am amazed as to how little he knows in the field. I can say this because I have interacted with very good and humble professors from top universities and seen the depth in their knowledge. In comparison, my supervisor is chalk, if they are cheese.
My supervisor is cunning. He maneuvers students and gives veiled threats if required. Forces me to publish in conferences which his friends or colleagues organize, even if they are not good.
He forced his Post Doc student as my another supervisor in order to fast track his career, without any kind of discussion with me. 


After two years, I have lost interest in my work and the passion has gone. All I do is push myself because I need to graduate. My creativity has no room and I hardly learn anything new. But on paper, I am progressing well because my supervisor had his way with me.

Now I have no interest in further continuing this association. I need to either quit my Ph.D. or look for another supervisor. If I do work with another supervisor at this stage, what could be the challenges?
Edit: I resolved my issue. I had a talk with the Dean. He told me about other students facing similar issues and offered me to help. He seems to have had a chat with my supervisor and suddenly I am offered more freedom. Another student had just switched because of the same reason and therefore my current supervisors had to change their attitude as this became a recurring phenomenon. The role of my primary supervisor has been substantially reduced. I have more say in what I wish to do and where I want to publish. And if I still do not like my environment it is possible to switch and school will help.
I have seen a lot of people switching advisers during my PhD. There are a few challenges I think you will face:


Your adviser, knowing his personality, won't let you go easily. He might tell other faculty there will be consequences if they take you as a student. It depends on his relationship to his colleagues and position within the department if he can make good of his threats. You should choose your future adviser from the faculty he cannot influence. If that is not possible, be prepared to transfer to a different graduate school. You may need to take a qualifier exam there again. They could also be happy to admit you if you have taken it already at your current school.
If you need to switch to a very different field, you should expect another 2-3 years as a beginner. You would graduate later. 
You seem to be already burnt out. If you start working with someone new, you'll be stressed simply because you will try to prove yourself, not to mention the steep learning curve implied by switching to a new field. It would be a good idea to take a vacation before.
Some departments have rules that limit the availability of funding from teaching assistantships once you have been long enough in the program. Make sure your new adviser can support you.
If you have family, you have to make sure they understand that you were forced to switch advisers and you might finish the PhD later. 


Given what you wrote, I believe switching advisers would be a good move. If you move within the same department, you have the advantage of knowing already who are the best advisers. If you don't, talk to their students and postdocs before switching.