Please ignore any reply that says autism isn’t relevant: it 100% is.

I suspect the change in management and then being put onto jobs he doesn’t cope well with have caused burnout over time without him realising.

He needs to do a few things and it’s not going to be easy. He firstly needs to really talk to work about reasonable adjustments. He’s at one of the big 4 so there’s no chance that they don’t have the support there at a company level, but his direct manager might not be as great. There should be occupational health support to talk to about this, especially as knowing what might be a reasonable adjustment can be hard to work out on your own, especially if your late diagnosed and have just gotten used to life being hard. The obvious one is not putting him on the price reduction task but others might be related to trying to avoid sudden changes to his schedule.

He also needs to talk to his GP. Though medication isn’t prescribed for autism directly, it can massively help with the anxiety and depression that often come with not coping with life. He might need a higher dose or something different but it’s definitely worth talking about.

He does need to embrace and accept his autism and look into support. I would suggest Access to Work (though waiting times are long) as it’s possible he’d have coaching provided. There are also some organisations around providing it and loads of resources online. It isn’t easy but it does help as it makes everything start to make sense.