Board Thread:Questions and Answers/@comment-29441363-20160811230119/@comment-28044177-20160813003924

Jam17692 wrote: when shinigami make their zanpakuto manifest themselves they can be made visable to others such as when renji made zabimaru manifest itself in front of ichigo and yoruichi

Not the same. Renji and Yoruichi saw Zangetsu because Ichigo was using the Tenshitai to manifest it. And the Tenshitai is visible to others. No one saw Zabimaru but Renji.