1. The above code is used int he single.php template (view for a post)
2. The filter value is loaded via $zone_articoli = get_field('zona_per_i_pacchetti');
3. The $loop find all pacchetto and ignores the filter
Perhaps you need to debug your code. Try removing the $zone_articoli from the equation and hard code the meta_query.
Also, is the select field a single or multi select?
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