It was a great trip.
I used the Z 400 mm TC as my primary lens on a Z9. Thom also had the Z 400 mm TC on a Z9 as his primary lens and used the Tamron 35-150 on a second Z9. I think he used the Z 28-400 on one of his Z9’s, when testing it, but he also had a Zf along, if memory serves.
The Z 28-400 is very small. I think it might be a decent choice for someone who wanted a relatively small, light one-lens solution with a large focal length range.
As I noted, I think Thom used the Z 28-400 on a Z9. That’s of course an odd pairing for most people. Heavy flagship body with small superzoom. I would guess it would be better choice with a smaller body, say the Z8, Z6III or the Zf.
Mark Comon co-led the trip with Thom. He used the Z 28-400 on the trip too.
Both Thom and Mark noted that the Z 28-400 was good for IR photography, as it had no hotspot.
Personally, if I wanted a lighter weight kit, I’d likely take the Z 24-120 mm and the Z 100-400 mm.