Create a nice story on how your experience as a developer is complimentary to your ambitions of being a product manager. Be data driven and have quantitative/tangible backup for everything you claim to have done. Sit down with PMs and learn their vocab, no the bookish one, but what they use daily.
Talk to your partner/ceo about it. If they aren't willing to help you transition, go to a startup. (serious)
Learn the ropes. Startups love people with ambition and drive, and care less about backgrounds (in non senior roles). You might be overworked but you'll get 3yrs of exp in 1. Then move to big tech/consulting.
While the work pressure may be high, bro, you're at EY it can't be worse.
And remember, engineer to product isn't career progression, it's a career change (and so is MBA)
Swallow that pill first, and then think about moving to the new role.