Takara and Hasbro are more like sister companies than rivals. Why do you suppose the upcoming Power of the Primes line by Takara is actually the same mainline figures that Hasbro has already put out in the west / Hasbro Asia.

Typo. I meant Bandai.

But what is wrong with it when it's integrated well? How is the Ninja Megazord any worse for having it?

This is pretty good news to hear, hasbro is one of those companies that tends to not screw up horrendously too terribly often.

I am okay with them having a monopoly on the toy market as long as the quality stays high.

Also, hasbro, do us a favor and release the final dino thunder zord we never got over here, the purple punching thing that I cannot spell.

The problem is it isn't always integrated well and even when it is it isn't really taken advantage of

The problem is that it isn't. They use it poorly, and they slapped ports onto figures just to force more intractability, making the designs worse for wear because of it.
The other problem is that ZB goes hand in hand with BOA's cheapening and oversimplification of the figures.

Wat did they mean when they said that Hasbro will hold the worldwide rights, excluding Japan and certain other Asian markets, effective as of April 1, 2019?

You're both missing the point. Clearly there were issues with the way Bandai implimented it, but the concept itself is fine. Why toss it out completely rather than just do it right?

Because it can't be done right.
The mecha aren't built to be universal, so forcing them to just brings more problems, either in forcing needless redesigns so that arms/legs can use it, or gutting gimmicks.
KyurenOh isn't designed in a way to accommodate ZB, unless they gut the electronics and make the Shishi Voyager's Kyutama ports come off for the ZB system.

That area is considered part of Japan's overall market, and thus Toei holds distribution rights for Power Rangers in those areas, and has selected Bandai Japan (and even Bandai America) for toy production/distribution.

Usually, Power Rangers is simply a dub name for the Sentai show, and the toys are all Bandai Japan imports.