From what I understand you have a seperate entity "Good" which is associated to an "Offer" which is associated to an account entity of the person who offers it or in the offer the ZIP code is saved of the person who offers it. Either way In the grid on the overview you could choose for a microflow as datasource and then first retrieve your current acocunt by the xpath:
By options choose "First" and by output I've chosen the name "CurrentAccount"
Then retrieve your offered goods by an xpath as follows when storing the zipcode of the person who offers it in the offer entity:
[MyFirstModule.Offer_OfferedGood/MyFirstModule.Offer/ZIPcode = $CurrentAccount/ZipCode]
or when you choose to connect the offer to the account of the person who offers it:
[MyFirstModule.Offer_OfferedGood/MyFirstModule.Offer/MyFirstModule.Offer_Account/Administration.Account/ZipCode = $CurrentAccount/ZipCode]
Here a modelshare of what such a microflow could look like: