The thing is not only don't we know that it was Ankhesenamun who wrote the letters - though she seems the most likely suspect - but we don't know Zananza was murdered, he could have broken his neck falling out of his chariot, died of dysentery, all sorts of things.

For all we know to the contrary Ankhes was conspiring against her grandfather's court party. Or she and Aye were conspiring together against Horemheb and his party. Or she Aye AND Horemheb were all partners against a conspiracy we know nothing about!

See why I love the tarpits?