Why Django Commands are working well outside the virtual environment and giving me errors inside virtual environment?

[ERIA JACKSON TALEMWA]

I recently installed Django on my machine, I installed virtualenv, virtualenv-wrapper and i even customized the ~/.bashrc file but;
Some commands like "python3 manage.py startapp" give me an error when inside the virtual environment but do work outside the virtual environment, I wanna know why?
why is it that django commands dont run in zsh shell but do run in bash shell?
Note:: Am writing all the commands in the folder containing manage.py and the django local server is already running

And please don't downvote my question because I really wanna know?

[Mariusz Felisiak]

Please don't use Trac as a support channel. Closing per TicketClosingReasons/UseSupportChannels.