And I'd rather have a male hysterectomy than a history male lecture me

I'd rather have a bottle in front of me than a frontal lobotomy.

HE CUT OUT HIS BRAIN, THAT BLOODY BABOON!

It struck me that he knew Zira was the top surgeon on humans, so he immediately questioned her. When she cleared herself, the pieces fell together as to why Zaius was so suspicious of him - because there had been a speaking human, until his brain was ripped into.

Yes, but I took it to mean he was asking her if she was involved, too. He said "They cut him.", so Taylor knew Zaius was involved immediately.

At first he questioned Zira, but she swore to him she had nothing to do with it. Then realization dawned on him and knew Zaius was responsible.

Yes, Zaius had heard Landon speak. That's why, as Zira said, "something is bothering him" and why he was snooping around the lab. Taylor knew exactly why Landon was lobotmized and who was responsible, which is why he went right after Zaius.

That's exactly what happened Zaius wanted to hide the truth

He told Taylor he'd always expected a speaking human to turn up.

Whether Zaius heard Landon speak or not, he had access to the sacred scrolls and knew of the history of man and ape so he knew it was possible that humans could speak.

That's wisdom, right there.

As my uncle use to say, 'I'd rather have a bottle in front of me than a frontal lobotomy'.

Zira pointed out that Zaius had been moping, and "prowling" around the lab. Undoubtedly he had heard Landon speak, either consciously or semi-consciously. My guess is he ordered the apes aware of it into silence before having him labotimized. Then suspected Taylor from Zira's reports.

Try reading the graphic novel 'Conspiracy of the Planet of the Apes'. Not a bad theoretical account of what may have transpired.
It wasnt me, it was the other three. Hang them!

Sounds right.