Flashing an actual PG32IMG.zip means the zip is signed with keys to validate it's from HTC. You renamed the .exe file to .zip. You might kill your phone trying things like that once you get S-Off and can flash unsigned images, so be careful. Your bootloader is the most risky part of your phone, so never act on guesswork.

You should be able to flash the exe file with your computer (providing you're running Windows). I'd redownload the file for the update you want and run it. It should give you all the instructions you need to continue.

From there, use the How-To threads here on the forums to get your bootloader S-Off.

If you have any more questions, you can pm me and I'll do what I can to help.
Having problems with root/S-Off on your DInc2? Visit my help thread here!

Device: Samsung Galasy S III
ROM: The Infected People's Rom
Kernel: Always the latest Anthrax
Recovery: TWRP 2.5.0.0
Baseband/Firmware: MD4
Device History:
HTC Droid Incredible -> Samsung Fascinate -> LG Revolution -> HTC Droid Incredible 2 -> HTC Evo 3D -> HTC Evo 4G LTE -> Samsung Galasy S III -> Samsung Galaxy SIV (In the mail!)