The problem is, I want to make the image zoomable on ODK Collect when form gets open, How can I achieve this in .xlsx file when designing the form. Where and how can I add big-image parameter in .xlsx file.
Welcome to the ODK forum, @Sonali! We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a picture as your avatar because it helps build community!
Displaying an image as media as part of the question.
I'm not sure if that is possible within Collect and XLSForm.
Could you use Android's Accessibility feature for Magnification?
big-image should allow you to click on the attached image and open and then zoom as well but I gave it a try and the behavior seems to be broken in ODK Collect...
I'm going to report the issue and try to fix it.