Finally found the answer for why the coordinates from Google Earth's KMZ are different on Google Maps projection.

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Its not correct to refer to WGS84 as a 'projection'. Rather it is a datum that is slightly different from a perfect sphere. WGS84 can still be projected onto a Mercator map (as in Google maps) or a sphere (as in Google Earth). You are simply going between mercator and spherical. Use the following functions to convert between the two.

(in PHP, should be pretty simple to express in a different language)

function latlng2xy($lat,$lng) {

$x = $lng;

$y = rad2deg(asinh(tan(deg2rad($lat))));

return Array($x,$y);

}

function xy2latlng($x,$y) {

$lat = rad2deg(atan(sinh(deg2rad($y))));

$lng = $x;

return Array($lat,$lng);

}

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