merge MOBI7 and AZW3

Hello to everybody!
It is my first post in this forum!

I just published a book in EPUB and I'm working on the conversion in Kindle Format.

I made two different files: a AZW3 that looks good and a MOBI7 that, after some changes, looks good.

Now I want marge the two files in one MOBI file to upload to Amazon, is it possible?

Gregorio