Filter in Visual - Column A and Column B Both = 0

Hi.  I'm really struggling with this one and have searched through several posts that on the face of it would appear to be the answer but I cannot make any of them work.

I have three tables:

Table A = Properties

Table B = Clients

Table C = Client Phones

Table A has a property phone number

Table B has a relationship to Table C which contains a phone number.

All 3 tables are linked in the data model and the rest of the visual contains various columns from related tables so the model seems to be working fine.

My Visual is a table and all I'm trying to do is export the resulting data to send to a team who will be contacting the clients.  But there is no point outputting a row if both the Property Phone Number and the Client Phone Number are invalid.  I'm in the UK and there shouldn't be a landline or mobile phone number that is less than 10 digits.

Here's a view of the visual:

I've created the two columns shown so that if length of phone number is less than 10 I return 0 otherwise 1.

The filter I need is to exclude rows where both Property_Phone_Length and Client_Phone_length are both 0.

Here's the code I've used to create those two columns:

Property_Phone_Length = IF(LEN('UMO300-Properties'[Property Phone Number])<10,0,1)
Client_Phone_Length = IF(LEN('UMO302-ClientPhones'[Client Phone Number])<10,0,1)

But all attempts to reference those 2 columns in a new column have failed.  Help please!!

Many thanks

David