If you want to do Dual Degree then you must have passed your 10+2 with more than 75% marks and if you can qualify JEE Mains and Advanced then you can do a Dual degree programme but in this case there will be no use of your Diploma in the entrance.

Also if you want to know an alternative way. Then you can go for Lateral entry exam after your Diploma and take admission in BTech. After completing BTech then you can sit for GATE exam through which you can get into IIT for MTech. In the lateral Entry examination you will be admitted in the 2nd year of BTech directly.

I hope my answer helps. All the very best for your future endeavors!