I'm not certain if Zenith had whole radios built by others, but they did buy parts from many manufactueres. They even brought lawsuits against some, claiming they were deliberately supplying defective parts to ruin the reputation of Zenith.
He is suppose to send me a picture of the tag on the chassis to confirm this... Doesn't say it was manufactured by Arvin.. just Zenith and Columbus, Indiana.... I live in Columbus... and have never heard of zenith ever having any facilities here... however Arvin made radios here for a long long time... and the headquarters was located here until the merger with meritor.... So I suppose I was just taking a guess that maybe arvin had done some manufacturing for them..