So, more about them pesky particles, the Proton.
Rather than be a surface feature/blemish like the electron, the proton is really something.
No, really, it is something!
That 'something' is a bit of ZPE, compressed/condensed into the thing we know and love as the proton.
But wait, there is more.
This 'knot' of ZPE didn't just plop out of nothing, it came from the vasty sea of ZPE, but it left a 'cavity'.
The knot is not really a separate entity from the ZPE, it is part of the general ZPE field, and the presence of the proton balances the cavity, in terms of total ZPE in the overall region.
OK, imagine the surface of a pond, but there is an arrogant bastard water drop that refuses to join to rest of the water.  You see this sometimes in vodka bottles: shake it up, tiny beads dance on the surface.  Same idea.
Here is the thing, though.  The 'beads' don't just dance on the surface, they displace it, make 'dents' in the surface.
If you have two beads, their 'dents' draw them together.  Just like gravity.
The more protons, the more 'dents' in ZPE, the more gravity.

What was the other thing...Inertia!
OK, if a proton 'dents' space/time, and large collections of these dents give rise to gravity, where does that leave inertia?
Well, consider that the proton and the dent are co-located.  If the proton moves at a steady rate, so does the dent.
But if the proton is accelerated, then something wierd happens.  The proton resists being accelerated!
I don't mean 'speed up' when I say acceleration, I mean change in velocity.
Why would this be?
The proton and then dent are 'linked' in a way where moving the proton moves the dent.  But the 'communication' of position is limited to V of C.
Acceleration of the proton would have to accelerate the dent as well, but the dent doesn't 'know' that the proton has changed velocity.
To simplify: It takes force acting on the proton to force it away from its dent, but that same force leads the dent to 'catch up' with the proton.
Greater acceleration required greater force, as the proton-to-dent 'offset' is greater.

Neutrons?  A proton that ate an electron.  Same other stuff applies.
Good night, and have a tomorrow.