Firstly check that your customer has a valid VAT number and add that to the customer profile. 
Both the buyer's and the seller's VAT number needs to be on the invoice. You can easily check the buyer's VAT number in the service provided by the EU (VIES VAT number validation).
Your add your own VAT number under My account -> Company information. 

1. Go the Invoicing tab, and choose New invoice.
2. When you choose a company Customer ->
3. -> the Invoice type will be chosen automatically by the system: Sales within the EU.
If needed, you can choose another language or currency for the invoice.  
4. The legal text in the footnote "VAT 0% Intra-Community supply of services" does not appear automatically, but you can add it manually.

Note that Zervant automatically removes the VAT, but if you exceptionally need VAT on this invoice, you can get it via "Visible columns" in the invoice editor settings, where you tick "VAT%".