The above camera is very good, and has a 32mm lens. The Z12 has a 64mm lens so distance to your capture point will make a difference.
Rain in particular isn't that big of a problem. Here's a 5231E-Z12E at 120ft in a pretty hard afternoon rain.
Of course it gets darker in thunderstorms so if running color, it does certainly darken the picture. Night will be similar, but actually less of a problem with external IR. I'll see if I can find an example, but we've been rather dry the past 30 days here..
Settings will have a lot to do with your image. Can you post an example snapshot of the problem you're seeing?
5231E-Z12E
View attachment HOA Entr_ch3_20200226153149_20200226153158.mp4
Snapshot of same car/tag on the 5231E-Z12E