In a separate post LAKIMAIJA has a first look at one of the 7x ZOIs and he first explains that the Zoi is different to the HRM-RUN in what it does. [You are encouraged to click that link to LAKIMAIJA as I am only using his information here].
The most important point is that, whilst the advanced/extended running dynamics of the Garmin HRM-RUN/HRM4-RUN tells you ‘stuff’, it doesn’t really tell you what to do about ‘stuff’ – other than inferring that you ‘make it better’.
Zoi tells you how after looking at running economics. To give you a flavour, the images below show where ‘Flat-Foot marching drills’ are specified after an analysis.
Images Source: LAKIMAIJA using chest-sensor, no data for image stance
This youtube clip is of the app which is already in the Apple Store approval process.
I think we are now looking at availability in Spring 2016.