I don't use zed or svelte, but this looks like the zed picture is missing a treesitter parser for svelte. Many editors have basic regex-based highlighting for many languages, and optional, more advanced, highlighting available through extensions. You may also get some semantic highlights provided by a language server if your editor uses the Language Server Protocol as well.

I found one extension from a web search. Did you try this? https://zed.dev/extensions/svelte

It's been a while, but from what I remember you need that extension for any highlighting at all, and that screenshot is with it installed. Also, if I recall, it's something about that extension using an outdated treesitter parser or something along those lines.