I was unclear:
The evolution of English has not been a linear development from a single origin. Regional, class and educational differences must have lead to a far wider variation in what we understand to be the 'English' of the 17th century than we have to cope with even today.
It's significant that early text books (including Thomas Lye's New Spelling Book of 1677) offered variations, to something as basic as the pronunciation of the letter Z, which had come to us via the French Zède who got it from the Roman Zeta, who in turn got it from the Greeks and possibly Phoenicians. Although these same sources are attributed as the rationale to the pronunciation 'Zed', it's also understandable that some scholars without verbal references might have chosen to offer 'Zee' as a more plausible alternative to a letter with these roots.
Either way it was not a hugely contentious issue at that time as neither, zoos, zebras, Zulus, zonkeys or zoom lenses were that common. Shakespeare in King Lear, has Kent scream at Oswald "Thou whoreson Zed, thou unnecessary letter!"
It's generally assumed, although not universally, that these 'minor variations' were seized upon in the post revolution enthusiasm to embrace anything that differentiated the new American citizens from the 'official' British Colonial position on nearly everything. So adopting the speech idiosyncrasies that still existed in perhaps west country migrants or even immigrants from non English speaking areas, was done in a hope they could quickly sound as different as possible to their enemies 'the English', who by then had officially adopted 'zed' as that was the version included in Samuel Johnson's first English dictionary of 1755.
The official American adoption of 'Zee' was confirmed by Noah Webster's inclusion in his 'Dictionary of the English Language' (1828 ); Z - It is pronounced 'Zee'.
