What exactly was the error message that you encountered? (Knowing exactly what it is might help in diagnosing the problem.)

If you were able to unzip the Juicebox-Pro zip file without any errors, then it is unlikely that the 'JuiceboxBuilder-Pro.air' file is corrupt or incomplete.
Please take a look at the Installation Issues in the JuiceboxBuilder User Guide to see if any of the troubleshooting tips help.

There is also a fairly comprehensive list of things to check and try in this forum thread.
Ideally, you should just be able to install JuiceboxBuilder-Pro by just double-clicking the installation file but as you are having difficulties, one of the suggestions in the forum thread (link above) might help.

If you continue to have problems, please post back with the exact wording of the error message you see so that I can hopefully help further.