Once you have set it up then adding Alexa TTS is not an issue.
There are folks on the Homeseer site already doing this with just running Python scripts.
Here short cutted this using HA to run the TTS speech and well events now.
It is really simple to do.
I am still in a learning mode and only testing with one DOT connected to the Russound system and mixing this with HS3 SAPI speech and another Alexa in the Kitchen. With said events you can talk to one specific alexa device or all of them at once. Now you can even tell which Alexa was used last in your home.
Baby steps here. Wife is used to the TTS from Homeseer of old BUT I am limiting the TTS to simple stuff...garage door, front door bell and sensors, et al. Over the years HS is not as chatty kathy as it was in the past and I am still using hard sensors connected to the OmniPro panel and now testing WiFi sensors using MQTT.
BTW here also use touchscreens to send commands out to the Alexa devices (as well as using VR).
The house here is a sandbox and it keeps me busy in my old age these days....
I am redoing my old legacy 1-Wire temperatures sensors (analog) to using MQTT these days. I have 1-wire sensors on the second floor covering the hallway, bedrooms and bathrooms and attic. I also have a hub in the basement covering main floor, outside, bathroom and rest of rooms on the main floor these days. Really a bit over kill as one sensor on each floor will do.
Here is the Homeseer 3 hourly chime that utilizes Microsoft SAPI running on an Oracle VB on the main HS3 Pro server. Doing now 5 different TTS fonts and speaker dot exe's here and hardly working.
You can do this moving your Zee2 lite OS to an Intel CPU running Ubuntu and Oracle virtual box as Oracle VB will not run on an ARM CPU at this time. IE: you can get a mini intel CPU with 4/8 Gb of RAM to do this except that it will be more costly than the RPi.
I have tried running QEMU on the RPi for Windows XP and it works but it is way to slow with the limited RAM on the RPI. It might work on a TVBox with 4Gb of RAM. With this you could run XPe and SAPI speech on the TV box.
With the TV Box prices at less than $100 you get much more for your money than an RPi and it is way smaller.
I priced the RockerPi4 with 4Gb of RAM, 32 Gb of eMMC, case and power supply at around $110 or the price of two TV Boxes.
Note here have 4 Windows servers, 4-6 Linux servers, 3 BSD servers running on Intel / AMD CPUs on the computer server rack.
Many Homeseer users are using one box with multiple CPUs and much memory to run multiple VMs (windows and Linux) these days.
Here my 15 HSTouch tabletop screens are running XPe and MS SAPI and they are totally controlled by HS (hardware and software these days). These also run Leviton OmniPro touch professional which is a bit limited but can be adjusted with the HAI touchscreen designer (a PITA to use).
I have modded these hardware wise and they run Windows (HSTouch), Linux (Squeezeplayers) and Android (but I do not use android for HSTouch).