Invoice under gst for reimbursable expenses by c & f agent

Facts of the case are :-

1. X a C& F agent is taking delivery of goods on behalf of importer Z .
2. X gets business of importer Z through Y.
3. X & Z does not know directly to each other.
4. X is also incurring expenses on behalf of Z  which are reimbursed by the middle man Y.

Which is the correct way of making invoice for reimbursable expenses by C & F agent

1. Can the Invoice for reimbursable expenses be made in the name of Y with his GSTIN no ie middle man?. if yes should  GST be charged on the invoice for reimbursable expenses as well.?

         OR

ii        Invoice for reimbursable expenses has to be made in the name of Z with his GSTIN ie importer then NO GST to be charged

          in the bill  as X is providing services as pure agent and hence the expense are incurred on behalf of the imported will not

          attract GST.

Can a person act as “pure agent” for more than one persons? In the above case can X act as pure agent for Y & Z?

Kindly give your views if it is correct or guide us further in the matter with your valuable knowledge and experience