Well, some spelling and grammar mistakes ("Babylonian's" for "Babylonians" - as someone with a degree in English, the use of an apostrophe to incorrectly indicate a plural noun is always grating) - and frankly the evidence isn't terribly convincing.
You are using tertiary (or even further removed) sources that say calculating the stars was something that the ancient Egyptians did well -- i.e. “The Egyptian men of old who had faithfully studied the heavenly bodies and had learned the motions of the seven gods..." (etc) comes not from the Egyptians and not from a contemporary Egyptian but from foreign sources who didn't document the source material or provide anything convincing. What does exist comes from a time after the Persians conquered the land (and later sources, after it became Hellenized.)
The 2nd Century CE sources could be used to support a claim for this being true for Hellenized Egypt, and given the big university at Alexandria, it is not an unreasonable assumption.
The math, likewise doesn't carry through. You can learn the principles of addition but this doesn't mean you will be applying the use of addition (to count your sheep and goats) to predicting the amount of harvest from the annual Nile Flood (in other words, a level of 10 feet meant that your fields would yield 30 bushels per acre.)
The "zig zag" function also doesn't imply that the Egyptians were using it or invented it -- they were in contact with the Babylonians and it's quite possible that they simply copied a clock from something that was a gift to the king and then modified it to fit their own needs. This could be done by simple observation and not by independent calculations.
Also, the Babylonians (who did use this method and were frankly the prime astronomers of the Levant) avidly studied the stars, made accurate tables, and used this information, constructing observatories and libraries for this information. We have no such artifacts that I'm aware of from Egypt. They made little effort to record the night sky to any great degree of accuracy -- because, frankly, they had no real use for that knowledge beyond "here comes Sirius, so the yearly Flood starts shortly."
The Babylonians lived in a ghost and demon haunted world. The stars were used to predict fortune and misfortune. The Egyptians did NOT live in such a demon haunted world (their dead protected them and helped them) and did not have a real need for astrology (and hence astronomy.)
Of the other great civilizations that developed good astronomy (Mesoamericans, China) the driving focus was on omens and predictions, not on understanding planetary motion.
So I'm not seeing any real correlation here - something that proved they were using this method and that it was so good that the Babylonians and others used it as a foundation in their own astronomy.
Your mileage, of course, may vary.
-- Byrd
Moderator, Hall of Ma'at