I do not believe there is a plug-in to do this that is still available.
The DNG on the Z1 would take considerably longer than 1s, likely closer to 10 seconds.
You can get a sense for the fastest interval for the webapi here:
If you use a plug-in, you can reduce the time for the JPG images.
This thread has information on using an early version of the plug-in with an older model, the THETA V. I haven’t tested this with the THETA X or Z1.