iirc, milaana heaters measure at 4 inches, splinter z/zion at 6.5 inches, and zion m at 12 inches (feel free to correct if wrong) - so the 2zm would have a heater length of approx. 8 inches?
perhaps the revised heater length will allow for better heater responsiveness and easier technique similar to the mi3, while providing the performance from the zion m
personally, i really enjoy the variability i can achieve with my zion m by using stems with open draw for light, flavorful hits or with draw restriction for thick clouds
some initial thoughts for improvement.. an adjustable intake might be nice and ive always wanted some sort of battery protection/off switch like the milaana, though im not sure how that could be implemented in the zion design