Humans probably can but generally choose not to. Most Zentradi living in human society live as miclones most of the time anyhow, Frontier is an exception in that it has space for full-size Zentran to live normally.
Though the possibility is always out there. In Plus we first meet Isamu fighting some disgruntled colonists using Zentradi powersuits. Who is to say they were all Zentradi in them?
Who knows, some humans might have even chosen to go off with Zentradi who chose not to live in human society and been Macronized to fit in.