All credit card clearance companies have strict rules about the methods webshop owners employ to verify credit card payments. This for obvious reasons of security.
Some webshop owners use EPOS (also known as EFTPOS) terminals - particularly if they have bricks-and-mortar shops where they sell their goods too, and what they do in this case is they make use of the OFF-LINE credit card systems.
Zencart has a built-in offline credit card payment module that simply captures the card details, splits it into dbase and email components (to avert having a full credit card number and its CVV transmitted over the internet) and then the data is sent to the shop owner.
The shop owner "BLENDS" the two pieces of info together (one from the dbase and the other from its matching email) then they run the payment through their EPOS terminal.
This is known as a CNP (Customer Not Present) transaction.
It requires that you have a merchant agreement with the relevant bank, and that they have issued you with an EPOS terminal.
BUT... as I say, they have strict rules about how these things are used.
Connor Kerr has written a Credit Card module that is a bit "safer" than the standard zencart one, but he is the first to advise that it is not entirely safe to use, and that by using it, users may be contravening their merchant agreements with their bank.
Some web hosts DO NOT permit offline CC modules to be used on shared servers.
Thankfully, there are alternatives. For safe ONLINE CC payments, you can easily set up systems such as Protx and PayPal. With huge numbers of people familiar with PayPal, I have found it to be an excellent way of taking card payments without the huge hassles normally associated with CC clearing by the big banks such as HSBC.
Furthermore, Zencart is now fully "verified" with PayPal and DrByte has devoted many long hours developing the PayPal module which works extremely well.
You will also be able to link your HSBC bank accounts to PayPal, so all in all, PayPal is a viable option.