Hello,
If all you want to do is zoom whole pages and have your zoom levels be remembered per site, Quickstyle can do that, supposedly. First, make sure a certain setting is enabled in Quickstyle's preferences. The prefs can be found in Safari's preferences dialog box, in the Extensions section, by clicking Quickstyle in the extension list. The setting that needs to be enabled is called "Take over ⌘+/⌘-/⌘0 keys for whole page zoom".
Having enabled that setting, you can just use the normal keyboard shortcuts for zooming a page (⌘+ and ⌘-), and Quickstyle will remember how much you zoomed on each site.
Or, anyway, it's supposed to. Just now I tried it on
developer.mozilla.org and it did NOT work. That is, when I pressed ⌘+, the page did not zoom in. Probably a quirk of the site. You may find other sites where it doesn't work. Any time if you press ⌘+/⌘- and nothing happens, you can at least use Safari's built-in zooming function by pressing Shift-⌘+ / Shift-⌘- instead. Your zoom level will not be remembered, but at least you can still zoom.
Oh, one more thing: Quickstyle can only "capture" the ⌘+/⌘- keypress if a web page has "keyboard focus". That means that whatever you type is "sent" to the web page. A web page will normally have the keyboard focus as soon as you open it in Safari, or when you switch to it. It will NOT have the keyboard focus if you're typing in Safari's address bar, or if you have focused a toolbar button by tabbing to it from the address bar. A way to guarantee that the web page has keyboard focus is by clicking anywhere inside it (except for a form field, in which case the field will have keyboard focus). This issue of keyboard focus is something not a lot of people know about, and sometimes they think an extension is not working (in terms of hotkeys) when the actual problem is that the web page does not have the keyboard focus.
Chul