What max aperture is the Zeiss.
Do you have a link to a specification?
I have a Sony A77 mk1 which is somewhat worse in low light than a mk2 so gives a guide.
In general terms the A77i is goodish at ISO 800, bearable at 1600 and usable at 2400 or 3200 if you value a usable image over noise. ie 800 would be daytime max if you cared somewhat. More at night may be OK.
If you use a tripod or solidly brace the camera then there is no sensible smallest aperture except for subject movement issues.
For night time street photography or static building shots etc f/1.8 is reasonably useful in a city with shop lights, good street lighting etc if you take great care.
f/2.8 about as good (1.8/2.8)^2 =~ 40% as much light
f/3.5 = 4x less light than f/1.8 = 2 stops and is getting reasonably marginal. Camera can be braced and you can Ninja breathe but any subject movement may reduce photos to more art-statements than records. You will sometimes get 'lucky' with moving subjects, but with the A77 you need as much light as you can manage.
Above that anything can work sometimes.
As for focal length. For street photography on APSC the 16-80mm is liable to work well in more situations than a 10-20mm. The latter of course has it's place but the wideness limits the range of things it is excellent at. – Russell McMahon 8 mins ago
I have put just a few night-time photos in this album as examples of either Sony A77 or the slightly noisier A700. All relevant settings shown where known.
These were selected by randomly jumping through a "RandomMaybes" folder and stopping at relevant night shots. No merit claimed for any except that I like them for some reason (in most cases :-) ).