I’m not a double star observer myself but I seem to recall that Zeta Her was often touted as a ‘fast’ binary (period 34.5 years). A quick internet search suggests the separation is currently 1.5″ but not changing significantly. However the PA is changing by 5deg per year so maybe that change is detectable over a period of say two years.
Your best bet is to contact the Deep Sky Section which has a double star group. Their Newsletters may also be of help here as they generally include double star info. The link is:- https://britastro.org/document_folder/baa-document-store/sections/deep-sky-section