Difference of implementations of fm modes between the reaktor and hardware

Hello! I'm trying to understand the difference of implementations of frequency modulation modes between the reaktor and hardware
What means exponential tzfm? And how to make it in Reaktor?
What means Thru-Zero FM/Thru-Zero PM - Thru-Zero PM is the same as exponential tzfm?

from Rubicon's manual:
TZFM EXP/LIN switch
- Selects the type of FM modulation the TZFM input will be.
This switch determines whether the response of TZFM is linear or exponential. The exponential setting is not really 1V/oct, and really just gives a
more extreme response to the modulation signal
but A100's manual talks: The most common exponential scale is 1V/octave. In this mode thru-zero is not possible as the exponential function cannot become negative.
Intellijel were wrong?
Also I found these

• Switchable linear and (for the first time in any module) exponential tzfm
• Linear index vca for dynamic control of tzfm depth

I'm not clear what that all means? What is it - response of TZFM is linear or exponential?
As I uderstand every synth have 1V/oct scale, I'm clear 1V/oct is for exp fm, but lin FM, lin tzfm and (what very interesting) exp tzfm - how??
What means exponential setting is not really 1V/oct?
How I can switch between linear and exponential tzfm in Reaktor?

 

read doepfer A-110-6

 

This simple patch shows you what's going on with Thru-Zero FM.

The 'FM' Knob controls the frequency in HZ of the second oscillator modulating the frequency of the first oscillator.

Send an A2 note and the scope is tuned to show you the waveform more or less synced with the Scope. You can tweak the msec knob in the scope to stabalize the waveform. This isn't exactly zero FM, but it is related.

Specifically, Zero FM means an oscilattor that accepts negative frequencies. What that means is that for a frequency F, a signal at at -F is 180 degrees out of phase -- in other words the negative/opposite.

In this example if you rotate it positive to (for example) 100hz and then to -100hz you'll notice that the waveform 'reverses' -- it's a mirror image. This is because changing the modulator in the negative direction inverts the modulator

 

Ok, thank you! But what what about exp TZFM?

 

Let me google that for you: https://www.native-instruments.com/forum/threads/exponential-fm.81072/

 

When I change FB the waveform moves forward and backward

 

Sorry, I can't understand why I need it and how I can use it
As I can see this thread about exp FM, that's alredy in Bento box, but I interested in exp thru-zero fm