Duration counter and air con zones for a dynamic dashboard

Hi All,
I have a dynamic dashboard that displays only what is on. It’s not using the “Auto Entities” functionality, it calls out entities specifically, as I only want certain things showing.
The code follows:

card:
  title: Whats on
entities:
  - entity: switch.aircon
    attribute: message
    type: custom:secondaryinfo-entity-row
    secondary_info: >-
      <i>Target Temp <style='color:gray'>[[ sensor.daikin_target_temp_4 ]]°c</i>
      <br><i>Current Temp <style='color:gray'>[[
      sensor.daikinap07452_inside_temperature ]]°c</i>

I’ve set up the air conditioning as an entity and I want to make two updates:
Firstly, underneath the current temperature, another ‘secondary_info’ – I simply want a duration counter – as in… The AirCon has been on for 2h 34m.
image

Secondly, I want to only show the active zones. Again, just as a secondary_info underneath the current temp. Above the next entity (in this case, above the pool heater).
In essence, I’m trying to put a nested entity-filter within the secondary_info of an entity within an entity-filter.
image

I have the full zone list in a card here:

image

But I don’t even want the switches in the secondary_info, just something like:
Air Conditioning
Target temp: 25c*
Current temp 25c*
On for 2hrs 34m
Active zones: Lounge & Kitchen, Hall

Current code for my full switchable entity list is here (showing all of them):

entities:
  - entity: switch.daikinap07452_zone1
    name: Master Bedroom
    toggle: true
    colorize: true
    hide_state: false
    full_row: false
    show_icon: true
  - entity: switch.daikinap07452_zone2
    name: Lounge & Kitchen
    toggle: true
    colorize: true
    hide_state: false
    full_row: false
    show_icon: true
  - entity: switch.daikinap07452_zone3
    name: Hall
    toggle: true
    colorize: true
    hide_state: false
    full_row: false
    show_icon: true
  - entity: switch.daikinap07452_zone4
    name: Rumpus
    toggle: true
    colorize: true
    hide_state: false
    full_row: false
    show_icon: true

Very grateful for any help, I’ve come so far learning from the incredible people here!