How to sync Health data from two different iPhones

How to sync two data sets in Health app

First off all I would like to thank Apple for outstanding products, ecosystem and support. I'm a big fan and a happy Apple's client no matter what pain (hours spent :)))) I have inflicted upon myself.

Now the bad thing:

I have accidentally deleted one of the devices listed inside Health app. This action caused the deletion of all historical Health data associated with this device (all my workouts and achievements in 3 years is gone). It was my mistake and I have no one to blame, but myself.

Fortunately, I do have a separate backup with the historical data which was deleted. I've restored this encrypted iTunes backup to my old iPhone and all the missing Health data is there! What a relief! (sarcasm)

Now, I do have two iPhones with the same iOS (16.3) and two different sets of Health data which I would like to sync together.

But after two days spent with Apple support it looks like it is absolutely impossible to merge the data from two devices!!!??? Really?! How can it be so?

My variables (iPhones have the latest iOS version installed - 16.3 ):

a) iPhone 13 Pro Max with Health data starting from Sep 2021 until today (Jan 2022);

b) iPhone 8 with Health data starting from Apr 2018 until Sep 2021;

c) Apple Watch Ultra with watchOS 9.3 installed;

d) Health data sync and store in iCloud is enabled for iPhone 13 Pro Max.

But after Health app sync to iCloud is being enabled in iPhone 8 (which holds restored historical data) follows this:

1) Health data from iPhone 8 starting to sync to iCloud (volume of Health data in iCloud is growing substantially);

2) After couple of hours (~3-6 hours period) all the Health data on iPhone 8 is getting gradually wiped out and being replaced by the data from iPhone 13 Pro Max.

Step 2 repeats every time when I'm restoring historical Health data on the old iPhone and enabling iCloud sync.

Historical Health data restored from iPhone 8 doesn't sync with iPhone 13 Pro Max.

I'm really sad and humbled by impossibility to merge two data sets using such advanced and modern technology.

I'm really looking forward to the solution how to get ALL my Health data whole again.

Thank you in advance!