You have not provided enough proof to link the 2 accounts. You should include here both posts showing they use same eth address. Tbh, I don't consider google forms as evidence because anyone can fill out the form with any eth address and bitcointalk account as they please. Most cheaters use other members' bitcointalk profile with their address to cheat a bounty campaign.

If you're really sure that  these 2 are cheating the mentioned bounty campaign (in the archive link provided), you should inform the bounty manager first.