Accessing Disk Images on iOS
To my understanding, the only workaround involves jailbreaking the iOS device. If you are willing to try that route, you might find this helpful: https://www.reddit.com/r/jailbreak/comments/4hgr0y/tutorial_mounting_a_dmg_on_ios/.

If not, I don't believe there is any other way to mount a .dmg on an iOS device.