I agree with you – the approach of the headline is interesting, but the original is probably a little too generic to really appeal to people.
I prefer your idea of getting your inbox to zero – that’s a far more specific benefit. I would swap around “proven” and “3-part”:
The Proven 3-Part Process to Get Your Inbox to Zero
A few alternatives:
How to Get your Inbox to Zero: A Proven 3-Step Formula
3 Simple Tricks to Get Your Inbox to Zero
My feeling is that a 3-part process sounds more long-winded than a 3-step formula or 3 proven tricks. It’s a subtle difference. But it’s worth keeping in mind that most readers are attracted to posts that offer easy solutions that don’t require too much effort.
Enchant readers. Woo customers. Win business.