My Short Answer
Despite the merits of Zeiss lenses, you should probably get the Sony 28mm f/2 FE. The cost is better (
$449 2017 MSRP versus
$1599 2017 MSRP), the weight is lighter (
7.1oz / 200g versus
1.39lbs / 630g), and the adjacent Sony lens lineup is broader (Sony E-Mount G Series vs Zeiss for Sony E-Mount / Zeiss E-Mount Lenses).
Note that the Zeiss lineup for the E-mount is concentrated in the 16mm to 70mm focal length range, and there is no macro lens (2:1 magnification ratio or better), no short-telephoto portrait lens (85mm+), and no telephoto lens (200mm+). These are key pieces in an advanced kit, and not having these offerings means you will pay a penalty in editing in the future if you have integrate lenses outside of the Zeiss T* coated family, as the color and rendition from lenses made by other manufacturers will deviate from images shot on Zeiss lenses. While much of this can be mitigated in post-processing, it's both a testament to Zeiss and an annoyance when editing images that their T* coated lenses have a particular look that is not matched by other lens manufacturers (due to Micro-Contrast, Citations: Ming Thein, Yannick Khong, Reference: Thom Hogan). Some additional Zeiss lenses are available with an A-Mount to E-Mount adapter, but you will lose autofocus capability on these lenses (See: Zeiss A-Mount Lenses).
Even with your intent to shoot at night and engage in astrophotography, some of the shortcomings of shooting at f/2 versus f/1.4 can be made up by investing in better supports (Barn Door Tracker for extended exposure times in astrophotography) and better camera bodies (better ISO performance on full frame bodies vs APS-C bodies). Plus, there are plenty of reviews that suggest that the 28mm is a very competitive offering by Sony (See: Sony FE 28mm F2 @ DxOMark vs Zeiss 35mm f/1.4 @ DxOMark, Steve Huff, Fred Miranda, Lonely Speck Photography).
However, if you are serious about not making compromises on performance, the Zeiss 35mm f/1.4 has two key advantages in low light:
Better light collection: The 35mm f/1.4 has a front diameter of 25mm, and the 24mm f/2 has a front diameter of 12mm. The 35mm will collect more than four times as many photons
(25/12)^2 = 4.34, resulting in better images in low light extremes. See: Low Light Photography and f/ratios @ Clarkvision. The 35mm can even be stopped down to f/2.8 (effective front diameter of 12.5mm) without sacrificing overall low light image quality
Better f/ratio: As mentioned in other answers, when wide open on both lenses, your exposure times will be half as much on the 35mm as they would be on the 24mm. A common exposure scenario at night is 1/100s at f/2 at ISO 1600. On the 35mm, you can expose at 1/200s at f/1.4, or improve your ISO to 800. This still applies on a tripod. Given an exposure of 4 versus 2 seconds, the 2 second exposure has less chance of scene movement (also mentioned in another answer, Ex: star-trails).
Anecdotally, Vignetting is supposedly better on the 35mm f/1.4, and Coma (when shot at f/2 or smaller aperture). However, I couldn't find any citations or obvious factors that would rule in favor of one lens or the other. It is unlikely you will be framing subjects in the extreme corners of a shot, and outside of the photon/light gathering capability, both lenses exhibit far less of these anomalies at f/2.8 or smaller apertures.
The Zeiss 35mm f/1.4 also has a better T-Stop rating (T/1.5 vs T/2, see Sony FE 28mm F2 @ DxOMark vs Zeiss 35mm f/1.4 @ DxOMark), but this is more a concern for filmmakers than photographers. You would have to shoot in very specific scenarios for this to matter for stills, as you will be shooting most shots based upon the light-metering measurements of your camera body, which will often vary scene-to-scene even more than the T-Stop to F-Stop difference of these lenses.
Zeiss lenses are expensive across all camera systems because Zeiss needs to make more money on each lens to justify offering a product (due to lower sales volume), because the build quality is better (all-metal housings), and because Zeiss offers features that others don't (integrated reversible lens hood mounts, aperture rings, aperture de-clicking on some lenses). Also, there's a little bit of strategy tax flexibility that Zeiss has due to having lens synergy and a broad lineup with consistent rendering in their T* coating ecosystem.
Last, if price is only a small concern, there is no reason you couldn't get both lenses. If you need to travel or walk a lot to get your shots, you can use the Sony 28mm for its weight and size advantage; and for most everything else you can use the Zeiss 35mm.