Woocommerce product is also a custom post type (product) only. you can easily write your own custom importer.
Each product may have the following structure
product - parent post
-- attachment - featured image, gallery
-- product meta - options, category, tags, price, stock ...
-- variation - product variants (it also contains options, price, stock...)
the importer flow will be like
createProduct() {}
uploadImages() {}
createProductMeta() {}
createProductVariants() {}
Woocommerce already has all the necessory codes you want, refer WP_PLUGIN/woocommerce/includes/api/class-wc-api-products.php
create_product( $data ) - line number 174
save_product_images( $id, $images ) - line number 1551
save_product_meta( $id, $data ) - line number 638
save_variations( $id, $data ) - line number 1080
trust me it's easy, i have already done that ( not for flipkart but shopify to woocommerce )