It seems like there’s some fundamental concepts that are being missed here (and sorry if this seems belittling. Not my intention)
First off, a file’s “type” is more than just the letters at the end. It’s how the data is stored. There are file types that are interchangeable, like anything that is just an ASCII text file such as .csv or .txt or (often) .log. These are interchangeable because the data is stored in the exact same way between all these file types. For these, you can simply change the letters after the “.” in the name to change file types. However, most files store information in a unique way designed to be read by a specific program. So for the vast majority of files, you can’t simply just change the letters after the “.” In the file name and expect it to work because the data in the file isn’t stored in the proper way.
Now, the .nl2pkg file is a file unique to NL2. It’s file structure (how the data is stored) was developed by the NL2 developers and is optimized for the kinds of files that NL2 uses. It contains all the information for a park as well as all of the scenery files and textures and scripts and everything needed to open that park in NL2. It is stored in a way that NL2 knows how to read. The information in the .nl2pkg file is stored differently than a .zip file (or .rar or .tar or .7z or any other compressed file format). You shouldn’t expect to be able to zip a file in Windows (or any other generic compression software), change the file type in the name to .nl2pkg and open it in NL2. .nl2pkg files need to be created using NL2 and read using NL2.
To get to your problem, what do you mean you “unzipped” a park and then “rezipped” it again? Did you do this using NL2 or just zip it with a generic compression software? What file type is your “zipped” park before you tried to change it?
