Converting shapefiles to .kmz's

[ChrisSlinko]

I have a shapefile that I converted  to a .kmz from it's native projection (state plane- NAD83).  A college compared my kmz to an older version of the same .kmz.  The two did not line up in Google Earth.  I spoke with and ESRI Tech support they said I should reproject the shapefile to WGS84 then it should line up in Google Earth well it did not line up with the older .kmz.  Both shapefile line up perfectly in ArcMap.  I don't know how the older version .kmz was created.  Does anyone have any suggestions on how they convert a shapefile/feature class into a .kmz/.kml?

Any info will help.

Thanks

[DanPatterson_Retired]

Start by not adding both files to the same data frame since ArcMap does projections on the fly meaning that if they are in different coordinates, they will end up "looking" like the coordinate system of the first-added file.
Add each to its own data frame...mouse around and look at the coordinate numbers...do they look like they are in decimal degrees?  If one is not, and it has biggish numbers, it is projected and you need to determine the projection of the file.  I think Google can do UTM but I am not sure.
Once you know what the files are, then project them to a geographic coordinate system ie. WGS84 so all the numbers are in decimal degrees.