Zen Cart Payment Module Development

I need a new payment module for Zen Cart created using API connections. The module must support multiple currencies.

API specification
Verifies callback authenticity
Updates order status based on payment result
Handles success, cancellation, and failure scenarios
Logs transactions for debugging

Requirements:
- API integration with payment gateways
- Support for multiple currencies
- Secure and reliable transaction processing

Ideal Skills:
- Experience with Zen Cart
- Strong API integration skills
- Knowledge of payment gateways and multi-currency setups
- Background in eCommerce security

Please provide examples of similar work done and ensure you are familiar with Zen Cart's architecture.