Hi Vinay, I did a little more checking and it seems there might be a way.  The ZT4 - 6 can create a printout up to 3.8 meters.  There are a few things it depends on though.
1. The most important is the DPI of the printer.  The 3.8 meter limit is only on 203 DPI printers, larger DPI means a larger bitmap and it will not be able to buffer as much bitmap. 
2. Don't expect the printer to be fast at printing this.  It will take time to process the image
3. The printer has to be set to continuous.  Depending on your actual label stock, this might not be ideal.  If there are pre-cuts or die-cuts already in the media, it is almost impossible to line these up perfectly at all times.  Use of a cutter on the printer would be more ideal.
4. Set the label length to your correct label length
5. The image data you send must be compressed or it will overflow incoming data buffer. 

Send the following to the printer to set continuous mode and label length(3 meters @ 8000dpm).  It only has to be done once per printer:
^XA^MNN^LL24000^JUS^XZ

Hi Vinay,
I'm not sure we've ever run across the use case of needing a printout this long, especially as an image. It must be a massive file.

The printer has  limit of a maximum length of 989MM.  The 'easiest' way to print longer is to break the image into smaller images with cropping tools in whatever platform you are using.  Set up the printer media type to continuous mode and label length to your cropped length - maximum 7912 (989 * 8). You might have to verify other settings like Label Home, Backfeed, Top of Form in order to ensure the image is printed smoothly.
Then you should be able to send multiple images in order as separate 'labels'.  As the printer is in continuous mode, it should print them back to back, so it will look like one long image.

Folks. please help me here.