The OP has a C-4 so the Hub Protection Service wouldn't offer migration. That's done (manually) via the Topic @bravenel made, which @ritchierich has suggested.
As @TechMedX suggests, we don't know what your goals are to make good suggestions, but for me, multiple hubs is a solution looking for a problem. Fortunately for me, I had problems that HubConnect solved. I've deduced that most/many Z-meshes are I/O bound, meaning they are a limited resource and more to the point, the resource is something we love to consume. We add devices as quickly as we can get them and some of them have extra features that can hurt in certain circumstances.. I'm thinking of power monitoring. The vendors default them to making power/voltage/current reports rather often. In no time at all, the Z-radios are processing very little other than power reports. That lead me to think about how to get more Z-radio bandwidth. Turning off chatty devices is one, but parallelism struck me early on as the answer. I limit myself to X devices per radio and even splitting my home into "upstairs" and "downstairs" sets of devices.
You can predict the future to some degree... most new devices will be introduced with S2. So you could start with using your C-4 for older non-S2 devices and use the C-7 for the newer S2 devices. You could split your home too.. maybe Front and Back or Left and Right. My point being, there's nothing obsolete in my collection of C-3s + C-4s + C-5s. They run my home quite well.
I tried a bunch of the time-saving, less impactful migration methods but eventually just did a complete manual migration.
Fired up C-7
Executed Z-Wave Firmware Update (C-7)
Made note of all the devices and apps configured on the C-4
Uninstalled all Apps (C-4)
Excluded all Z-Wave Devices (C-4)
Included Z-Wave Devices (C-7)
Remove all Zigbee Devices (C-4)
Add Zigbee Devices (C-7)
Removed all LAN and Cloud Devices (C-4)
Added all LAN and Cloud Devices (C-7)
Factory Reset and Shut-Down C-4
Began installing and configuring apps
When removing Z-Wave and Zigbee devices from the C-4 I started with the battery (non-repeater) devices and then went to the devices furthest away from the C-4 working my way inward.
Where there were issues excluding devices using the C-4, I used the device factory reset instructions to ensure it was properly excluded and ready to be included with the C-7.
When including Z-Wave and Zigbee devices with the C-7, starting with non-battery devices closest to the C-7 working outward followed by including battery devices.
A few times during the process of including Z-Wave devices I stopped and ran a Z-Wave repair.
When including Z-Wave devices with the C-7, only employed Z-Wave security with locks, garage doors, and security devices.
Obviously this approach is quite time consuming and I'm still slowly rebuilding my automations. Was it worth it all? I don't know. Things seem more stable and faster but that might just be a placebo effect similar to how you think your car is faster after its been detailed.
One unexpected benefit. My wife realized she prefers home automation that occasionally has issues over no home automation which has resulted in Alexa and me receiving far fewer curses, but this may also be a placebo effect...
@bobbles I thought I'd try your process, but when I restore my new C7 with C4 backup, my C7 hangs at 60% upon reboot. Any ideas as I like your process much better than @glenn which is basically starting from scratch.