You should definitely choose the Nikon NIKKOR Z 24-120mm f/4 S for your Italy trip! Its an amazing, versatile lens that outperforms the 24-70mm for travel.

• The 120mm reach is fantastic for distant street subjects.
• Lighter weight makes it way better for all-day tours.
• Optical sharpness is incredible at every focal length. Dont worry about f/4... the Z6ii sensor is fantastic in low light anyway!

Saw this earlier and had to jump in cause I went through this exact same spiral before my last trip. Quick question tho, are you planning on mostly outdoor night street shots or are you talking about dark museum and church interiors? It kinda changes how much that f/4 is gonna hurt. Honestly I was pretty disappointed with my kit after my last big vacation. Here is how I see it:

• The Nikon NIKKOR Z 24-120mm f/4 S is amazing for detail during the day, but unfortunately f/4 really let me down once I hit those dim restaurants. I ended up with way more noise than I wanted.
• I checked out the Nikon NIKKOR Z 24-200mm f/4-6.3 VR as a cheaper option but it was just not as sharp as expected at the long end. Total bummer.
• The Nikon NIKKOR Z 28-75mm f/2.8 is alright for the price, but it feels a bit 'budget' compared to the S-line glass. If you are worried about the budget, maybe grab the 24-120 and then a super cheap Nikon NIKKOR Z 40mm f/2 for the evening? That little prime is a lifesaver in low light and it wont break the bank like a 2.8 zoom would. Just a thought since buying used can be such a gamble...

^ This. Also, I've shot quite a bit of travel over the years and while that 120mm reach is nice for compression, f/4 can feel really limiting once the sun goes down in Europe. Those narrow side streets and old churches eat light for breakfast. I'd actually suggest looking at the Nikon NIKKOR Z 28-75mm f/2.8 instead. Its basically the perfect middle ground for your budget since you can find it brand new for under a thousand. It lacks the S-line badge but honestly the optics are solid for travel. If you absolutely need that 120mm reach tho, maybe pair the Nikon NIKKOR Z 24-120mm f/4 S with a tiny Nikon NIKKOR Z 40mm f/2 for those evening receptions. In my experience, relying on f/4 in truly low light usually means cranking the ISO way higher than I'm comfortable with, even on the Z6ii sensor. Just something to weigh before you pull the trigger.

^ This. Also, I've been incredibly satisfied with the Nikon NIKKOR Z 24-120mm f/4 S as a one-lens solution. Looking at the MTF curves, the resolution fall-off at 120mm is actually negligible compared to most travel zooms, which makes me happy when I'm cropping into street shots later. I used it during a dusty shoot in the desert last year and the weather sealing data isnt just marketing talk... it really holds up well in the field. No complaints about the autofocus speed either, even when tracking subjects in lower contrast light. One big warning tho... dont go buying those gray market lenses just to save a few hundred bucks before your trip. I had a buddy who tried that for a vacation and the lens mount had a slight alignment issue that basically ruined all his wide shots. Since it was an international version, Nikon wouldnt touch it under warranty when he got home. Honestly, its a huge gamble with reliability when you need it most. Also, be super careful with cheap generic filters. I've seen some really nasty ghosting and flaring from poor coatings that can basically negate the high-end glass you're paying for. Its better to go filterless than to put a cheap piece of glass in front of an S-line lens. Just stick to the official gear so you dont have any regrets while you're in Italy.