Indeed. If you were able to extract the Juicebox-Pro zip file without any errors then it's unlikely that your JuiceboxBuilder-Pro.air file is corrupt.
Your SHA256 checksum is correct for JuiceboxBuilder-Pro v1.5.1. However, there is a slightly more recent version (technically v1.5.1.2 but still labelled as v1.5.1 within JuiceboxBuilder-Pro) which you might like to try.
You can download it using your original download link. Upgrades are free within the same major version number you purchased and download links always point towards the latest version rather than the version you purchased. If you can't find your download link or it has expired, then please fill in the Download Link Request Form and we'll send you a new one.
You'll find checksums for the v1.5.1.2 zip and AIR files here.
If this does not help, then there are some hints and tips in the 'Troubleshooting JuiceboxBuilder installation and usage problems' forum post here.
The suggestions in the post which I think may be most relevant to your problem are #4 (regarding the location of the JuiceboxBuilder installation file), #9 (regarding anti-virus programs) and #10 (regarding the system clock).
#4 Make sure that you have actually extracted the 'juicebox_pro_1.5.1.zip' file to your hard drive (rather than just looking inside the file with a zip program or with Windows File Explorer) and that you are not running the 'JuiceboxBuilder-Pro.air' file from a restricted file system or network drive.
#9 Try completely disabling any third-party security software that you might have installed (e.g. Avast or AVG), including real-time protection and ransomware detection, before attempting to install JuiceboxBuilder-Pro in case this may somehow be interfering with the JuiceboxBuilder-Pro installation. (Please do so at your own risk and be sure to disconnect from the internet first.)
#10 Check that your system clock is accurate (and resync with a known time server if necessary) before attempting to install JuiceboxBuilder-Pro. (One user actually claims to have had to wind back his system clock 2 years in order to install JuiceboxBuilder-Pro. This seems to have been an isolated incident and no-one is quite sure why this was necessary but it might be something worth trying if nothing else works.)
Can I expect this to work fully?
It's certainly not something I'd recommend but I think it should be OK.
As far as I am aware, the JuiceboxBuilder-Pro installer does not add any entries to the Windows registry so as long as all the files are in place, things should work OK.
Please note that this is not an official 'yes' and it is untested but I don't foresee any problems with it (other than the lack of an automated shortcut and uninstall entry).
Hopefully my notes above will help you to install JuiceboxBuilder-Pro using the regular AIR installer file.
Please let me know how you get on and if I can be of any further assistance.
Thank you.