The branch change solely depends on the branch's strength. You have to score well in both CSE and ECE to make them believe you are talented and can handle all challenges smoothly. Getting equally good scores in subjects from both branches might improve your chances of branch change. However, sometimes issues related to batch strength become a big hindrance to branch change. According to the policy, the branch you are shifting, or the branch you are shifting, if they get their new strengths violated by 10% of the total seats in that branch, they are not allowed to change. But this is something that is beyond your control. I had a friend who could change his branch to CSE with an 8.8 CGPA while another failed to get a branch change despite a perfect 10.
Don’t let this demotivate you and concentrate on remaining at the top of your branch.