The Zapier/Ezekia method ‘Find Custom Field Values’ gives you all the custom values for the record involved, however the required value is difficult to extract from this list as there could be any number of custom fields, and they could be presented in any order.
The easiest solution is to use the Zapier function 'Code by Zapier'. Choose the 'Python' action event. It needs to look something like this screenshot.
There is an attachment at the bottom of this page - you will need to open the page full screen to see it.
Copy and paste all the text in the attached file into the 'Code' box at the bottom of the panel, removing any previous contents.
Add the following four fields as parameters (there will be one field ready to be filled in, so you will need to add three more). The field values are shown below. The bold value goes in the box in the left (make sure you get the exact value, with no extra spaces included), and you need to select the appropriate field to use as shown in the box on the right.
inputNames – use the 'Custom Field Label' field from the 'Find Custom Field' step.
inputValues – use the 'Value' field from the 'Find Custom Field' step.
inputValueCounts – use the 'Value Count' field from the 'Find Custom Field' step.
inputSelect – just type in the exact name of the custom field you want to retrieve.
When you test the step, the value of the custom field you want will be returned in a field called 'Value'. If no matching value is found, it will say ‘none’.