When I lookt up the definition of zeugma to confirm that I'd correctly identified it, Merriam-Webster's observation that "Zeugma... is economical: it contracts two sentences into one" made me realize something else. This verse describes how people will have to ration their food and water, and zeugma's reuse of sentence elements illustrates this saving in a grammatical way. Rather than two clauses ("They shall eat bread by weight, and they shall eat it with anxiety"), they're combined into one.
Then I started wondering whether this structure is in the original Hebrew. I've been reading The Lutheran Study Bible, which uses the English Standard Version. The New International Version has the more prosaic "The people will eat rationed food in anxiety and drink rationed water in despair." When I referenced the STEP Bible, I discovered that the Hebrew text does have zeugma:
וְאָכְלוּ־לֶחֶם בְּמִשְׁקָל וּבִדְאָגָה וּמַיִם בִּמְשׂוּרָה וּבְשִׁמָּמוֹן יִשְׁתּֽוּ׃Here's a link to the interlinear.