Lets Examine the Myth of Zoroastrianism being the First Monotheistic religion  :

Date of Zoroaster:

Zoroaster Date

:18th Century
:10th Century
:6th century BCE(Yup A Hundred Years Before Cyrus)(From Wokrs Of Ammianus Marcellinus 6.32, 4th century CE)
:James Darmesteter Says its c. 100 BCE

There is no evidence of His existence so the Dates among Iranists are from Mythological Sources

Besides lets See what Tabari Says: Zaradusht bin Isfiman (an Arabic adaptation of “Zarathustra Spitama”) was an inhabitant of Palestine, and a servant of one of the disciples of the prophet Jeremiah. According to this tale, Zaradusht defrauded his master, who cursed him, causing him to become leprous (cf. Elisha’s servant Gehazi in Jewish Scripture).

The apostate Zaradusht then eventually made his way to Balkh where he converted Bishtasb (i.e. Vishtaspa), who in turn compelled his subjects to adopt the religion of the Magians.

Recalling other tradition, al-Tabari (i.681-683[44]) recounts that Zaradusht accompanied a Jewish prophet to Bishtasb/Vishtaspa. Upon their arrival, Zaradusht translated the sage’s Hebrew teachings for the king and so convinced him to convert (Tabari also notes that they had previously been Sabis) to the Magian religion

When Alexander had conquered Persia in  330 B.C.E the Greeks had introduced a ”Age of Alexander”,since the Parsi Preists were nt Happy About this they had Introduced a ”Age of Zoroaster”they concluded he must have lived “258 years before Alexander.”

however the linguistic aspects of the Avesta only show it could have been from  Circa the Eleventh Century B.C.E

the 6000 B.C.E Date is mythological.

and the Monotheists such as   King Nabi Dawood(i.e King David)and King Nabi Sulayman(i.e Solomon)show there had been a monotheistic religion before this time because they were from the 10th Century B.C.E

and this was also known as Eshlam(i.e. Islam)the builders of the first temple being known as muslimai(i.e Muslims)and this was built in 1000 .B.C.E

http://www.youtube.com/watch?v=mfByvw_jomo ”Jewish Rabbi admits Islam is the oldest religion ”

Amenhotep (Circa 1348/1346 B.C.E )had made Aten the supreme monotheistic diety of Egypt and Forbade the worship of other gods.

and recent research suggests the Semitic peoples of Mesopotamia had a monotheistic religion,and Gradually turned to Polytheism

http://www.thestoneage.org/stone_age_03.php

the Article is Called  :

Five years later, Langdon would state in The
Scotsman as follows:
The evidence points unmistakably to an original
monotheism, the inscriptions and literary remains of
the oldest Semitic peoples also indicate . . . monotheism,
and the totemistic origin of Hebrew and other
Semitic religions is now entirely discredited

Excavations at modern Tell Asmar, the site of a
Sumerian city dating from 3,000 BCE, unearthed findings
that completely corroborated Langdon’s ideas.
The excavation director, Henry Frankfort, gave this
official report:

In addition to their more tangible results, our excavations have established
a novel fact, which the student of Babylonian religions will have
henceforth to take into account. We have obtained, to the best of our
knowledge for the first time, religious material complete in its social
setting.
We possess a coherent mass of evidence, derived in almost equal
quantity from a temple and from the houses inhabited by those who
worshiped in that temple. We are thus able to draw conclusions,
which the finds studied by themselves would not have made possible.
For instance, we discover that the representations on cylinder seals,
which are usually connected with various gods, can all be fitted into a
consistent picture in which a single god worshiped in this temple
forms the central figure. It seems, therefore, that at this early period
his various aspects were not considered separate deities in the
Sumero-Accadian pantheon.

Frankfort’s discoveries reveal very important facts about how a
superstitious, polytheist system comes into being. The theory of the
evolution of religions claims that polytheism arose when people
started to worship evil spirits representing the
powers of nature. But it was not so. In the
course of time, people developed different
understandings of the various attributes
of the one God, which
eventually led to distortions in belief
in one God.

the one God turned into the belief in several.
Long before Langdon had made his translations of the
Sumerian tablets, a researcher by the name of Friedrich Delitzsch
made similar discoveries. He found that the numerous deities in the
Babylonian pantheon all devolved from the various characteristics
of Marduk, as they called the one Deity that time. Research has
shown that belief in Marduk resulted from the deterioration, over
time, of the belief in one true God.
This one Deity, Marduk, had many names. He was called Ninib,
or “the Possessor of Power,” Nergal or “Lord of Battle,” Bel or
“Possessor of Lordship,” Nebo or “the Lord of the
Prophet,” Sin or “Illuminator of the Night,” Shamash
or “Lord of all that is Just,” and Addu or “God of Rain.”
Over the course of time, it seems that the attributes of
Marduk became detached from him and assigned to
different deities. In the same way, false deities such as
the Sun-god and the Moon-god came into being as
the products of peoples’ imagination. Belief in
Marduk, along with the other names of this false
deity, shows that this belief system actually developed
over time through distortion of belief in
the One God.
We can also see traces of such perversion in
ancient Egypt. Researchers have discovered that
the ancient Egyptians were first of all
monotheists, but that they later dismantled
this system and turned
it into Sabeism, or sun-worship.
M. de Rouge writes:

It is incontestably true that the sublimer portions of the Egyptian religion
are not the comparatively late result of a process of development
or elimination from the grosser. The sublimer portions are demonstrably
ancient; and the last stage of the Egyptian religion, that known to
the Greek and Latin writers, heathen or Christian, was by far the
grossest and the most corrupt.
The anthropologist Sir Flinders Petrie says that superstitious,
polytheistic beliefs emerged through the gradual corruption of belief
in a single deity. In addition, he says that this process of corruption

can be seen in present-day society as well as in societies in the past:
There are in ancient religions and theologies very different classes of
gods. Some races, as the modern Hindu, revel in a profusion of gods and
godlings which continually increase. Others . . . do not attempt to worship
great gods, but deal with a host of animistic spirits, devils. . . .
Were the conception of a god only an evolution from such spirit worship
we should find the worship of many gods preceding the worship
of one God . . . What we actually find is the contrary of this, monotheism
is the first stage traceable in theology. . . .
Wherever we can trace back polytheism to its earliest stages, we find
that it results from combinations of monotheism. . . .

(See:73. Stephen H. Langdon, Semitic Mythology, Mythology
of All Races, Vol. V, Archaeol. Instit. Amer., 1931, p. xviii.
74. Stephen H. Langdon, The Scotsman, 18 November
1936.
75. H. Frankfort, Third Preliminary Report on Excavations
at Tell Asmar (Eshnunna): quoted by P. J. Wiseman in
New Discoveries in Babylonia about Genesis, London:
Marshall, Morgan and Scott, 1936, p. 24.
76. P. Le Page Renouf, Lectures on the Origin and
Growth of Religion as Illustrated by the Religion of
Ancient Egypt, London: Williams and Norgate, 1897, p.
90.
77. Sir Flinders Petrie, The Religion of Ancient Egypt,
London: Constable, 1908, pp. 3, 4.)

source