Hi pkolomeits, CUDA upgrade is planned for a future JetPack-L4T release. There isn’t yet a definitive release timeline for the new version.
The distributable of ZED SDK v2.4 built for Jetson is based on JetPack 3.2 and CUDA9, it is provided by Stereolabs here: https://www.stereolabs.com/developers/release/2.4/
You don’t necessarily need JetPack’s CUDA toolkit on the host, it is just used for cross-compiling the CUDA and VisionWorks samples (which you later can build yourself onboard the Jetson) and Tegra profiler. However if you aren’t using these, you can disable the JetPack install of CUDA toolkit on the host PC, in the JetPack GUI (you will still want to install CUDA toolkit to the target Jetson). This then frees you up to install another version of CUDA toolkit on your host PC.