Restoring emails/chat from Google TakeOut backup to a different account

I have a Google Takeout backup of my former work account (which I no longer have access to). I've tried some free tools to restore the emails and google chat history but none seem to work, and Google doesn't have a tool that I can find. Am I able to somehow put the emails in a readable and searchable format?

for context: I'm in a legal dispute with my former employer for holiday pay that I'm entitled to. In response, they're making a pretty underhanded counter-claim, stating that they had "accidentally" over-calculating the bonuses I earned for 2 years. The actual correct (and historic) bonus structure was based on either an email or GChat message I received shortly after I joined. While it's not 100% concrete evidence, it would be an improvement over my word vs. theirs (as apparently good faith has broken down a lot)

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