You might have an easier time asking about that in the LNP thread. It's probably a dfhack plugin since neither vanilla 34.11 or 40.18 behave that way. If that's the case, implementing it in MDF could be problematic if the plugin needs customization to get it to work properly in MDF (meaning you can't necessarily plop an updated .dll into MDF and expect nothing to break).
I expect it may have been implemented in an update for a plugin used in MDF, but after the last MDF release, since there is only a couple plugins in LNP that aren't in MDF, and of those, the only one that might have anything at all to do with the display is dfterm (and I doubt even that since that's more about multiplayer functionality than GUI). More probable are updates to rendermax or text will be text but I wasn't able to find reference to zoom functionality in those threads (I didn't look very rigorously), nor am I sure exactly what version of those plugins are used in MDF versus LNP.
But anyway, yes, I suggest asking in the LNP thread what the source of that functionality is. Once that's known, you can look into how it might be ported into MDF on an individual basis.
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Heh, forget all of that. It's definitely Text Will Be Text, but it appears to require a more recent versions of TWBT (and dfhack) than is in the most recent MDF release.
I'm going to try manually updating dfhack and TWBT to see if things break.
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So yeah, you can try updating dfhack to r5 and getting the most recent TWBT that works for df.34.11/r5, but doing so is going to break some other plugins (there were only three warnings in the dfhack console, plus rendermax throwing an error rather than just a warning) since those are built for dfhack.r4 and not r5. I didn't go any farther but, in theory, if you update those as well things might work. On the other hand, it might not. ¯\_(ツ)_/¯
Might be more effort than it's worth, depending on exactly how much you need to be able to independently zoom the game view from the menu text.