Will the contents of a password protected Zip 2.0 file be safe for a week I will need to distribute a file to people for a challenge and I need them to open the file at the same time. The file will be provided a couple of days before the challenge. For maximum compatibility (so no need for 3rd party software, just OS supplied tools) I was thinking of using a password protected Zip 2.0 file.

After some reading I think this will be OK, but I'm not sure. I can't seem to find information on my specific use case (the file only needs to be secret for a short amount of time).

There will be only one file and I will use a 5 word diceware password to make it easy for entering the password while keeping quite a bit of enthropy.

Will this keep my file secure for about a week, assuming people don't have access to big computing clusters?
I just stumbled on http://www.tomshardware.com/reviews/password-recovery-gpu,2945-5.html. Although it's a bit old, it does give me some perspective. It mentions ~30 million password tries per second on a Zip 2.0 file. So if someone had a that can perform 10 times as much tries per second, they would need (6^5)^5 / 300 000 000 = ~94767626766 seconds = ~3000 years. I don't think anyone will be spending time and money on a 200000 node cluster to bring this down to ~5 days.

@SEJPM, thanks for your comment that gave further thought to my own question. I was wondering, how did you come up with 2^44.8? If I calculate (6^5)^5 / 7 / 24 / 3600 I get 2^45.4. Is there a something I'm overlooking?