Changing App Installer to Flashable Installer?

Hello There Everyone!, To clarify the title... Is there a way to change, modify, convert, etc... an App Installer (.apk) to a Flashable Installer (.zip). I'm not referring to just creating a zip to simply copy the apk file to its desired directory but, to either install the app as a new app and/or upgrade an existing one in the same/similar fashion as would an apk itself would be installed. I tried to search around and the results aren't specific to what I'm asking and reflects the copying of the apk file rather than the installing of it. I hope that I had explained this okay via text... :-) Thank you very much for your time and understanding with this question! ~Ibuprophen