Hello,
We are a team of software engineers with 6+ years of experience in professional software development.
We would create a desktop application in Delphi to perform the required processing and zipping/unzipping, it would have no external dependencies and would work on all Windows versions, XP and onward.
The fact that extension is different than .zip is of little importance, if the file is in a zip format we would be able to extract and later package it again easily. We would also make sure that it stays in the same zip format, so that it can be read by the other app.
As for the reordering of the contents, if I understood correctly it is a xml file that is zipped, and it contains the math formulas. We would create a intuitive user interface that would allow you to manipulate and re-order the formulas before putting together the xml again.
Based on your more detailed description and/or sample files we are available for creating a small demo for you to test before you accept our bid.
Let me know if you are interested, we will discuss the details.
Regards,
Filip
CodeStream