Sezzle / Zip BNPL for WooCommerce lets US and Australian merchants offer two more buy-now-pay-later choices alongside Klarna and Afterpay, so BNPL-preferring shoppers find their familiar lender at checkout instead of abandoning the cart. This is a build-to-order plugin — ECOSIRE develops it against your live Sezzle and Zip merchant accounts, installs it on your WordPress site, and supports it after launch. There is no instant WordPress.org or WooCommerce.com download.

We register each provider as a proper WooCommerce payment gateway (WC_Payment_Gateway subclass), wired into the Checkout block and classic shortcode checkout. Each gateway authorizes against the Sezzle and Zip merchant APIs server-side, redirects the buyer to the lender's hosted approval flow, then validates the return and webhook callbacks before WooCommerce marks the order processing. Settings live in WooCommerce → Settings → Payments, with sandbox and production API keys, currency gating (USD/AUD), and per-gateway enable toggles.

On-site messaging renders pay-in-4 widgets on the single product page (via woocommerce_single_product_summary), in the cart and on the checkout review, using each provider's official messaging script and your real cart total — no fabricated APRs. Eligibility rules hide a method when the cart falls outside the lender's supported min/max order value, restricts by shipping country, or excludes specific product categories.

Refunds and reconciliation run through the WooCommerce refund UI: a full or partial refund calls the provider's refund endpoint and writes the lender reference into order notes. The build is HPOS-ready (custom order tables) and respects WordPress hooks/filters so your theme and other extensions stay intact. WPML/multisite and translated messaging strings are supported on request.