Hello aspirant,

i hope that you are doing absolutely great.

With reference to your above mentioned query, i would like to tell you that YES, you can do both Diploma and class 11th at the same time, but it depends on the university also.  You cannot do two full-time courses together. So, one has to be in full-time and other in distance mode or both via distance mode. It is also not easy to concentrate on both.

For more information about diploma courses you cna follow the below mentioned link : https://www.careers360.com/courses-certifications/online-degree-diploma-courses

I hope that this will help.