Until the Twitter sidebox Cached plugin is updated by the developer to be compatible with Twitter's API 1.1, you could embed a Twitter timeline into your Zen Cart website (this is what Twitter recommends). More info here: https://dev.twitter.com/docs/embedded-timelines

Potentially, you could create a custom sidebox featuring an embedded timeline. Instructions for making a custom sidebox here: http://www.zen-cart.com/wiki/index.p...Custom_Sidebox