Hi @Magnus_P
First of all: Happy wife, happy life! 
Do you have Zaptec go oder Zaptec Pro boxes? If I remember right, Zaptec offers an integrated dynamic “overall” loadbalancing, that makes sure, that you never go higher than 16A oder 32A (depending on your house installation) on your over all house installation. But this servie is not available for “go” boxes as far as I understood my Zaptec Dealer. They are thinking to offer this in the future. What ever this means.
How are your 2 wallboxes configured right now? Are they both allowed to charge with 3x16A? or how do you handle this today? This should be visible at your Zaptec Webportal.
As you can see, my box is limited (this is a physical switch in the hardware) to 16A What ever i would set manually with the loadbalancing toolset, it never goes higher than 16 A. How is this setting on your 2 installations?
If both boxes are allowed to be set to 16A you theoretically can now build your own "overall loadbalancing with Homey: You should be able to set each wallbox it’s own values. If you build flows, that sets one box to a lower Ampere Output and the other one to a higher Ampere Output you will have the same effect as Zaptec “Pro” would do. BUT: You have to be carefull with that, If one flow fails or if you don’t have enough time buffer in between, your house will be dark 
I would be careful with that.
Hope I addressed your question with this?
