Hi,
I want to recommend to use a mass action but it would have some constraints.
You can create an action to delete all products which have a specific "product_vendor_id".
So each time you delete a vendor, you have to note his ID and then execute the mass action with the targeted ID.
Cause of open issues ; HikaMarket do not have the possibility to have a dynamic integration with mass-action system ; I hope that the HikaShop team will fix it so it would open a lot of new possibilities in that system.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.