Appendix G: zap tag on other events
When an event includes one or more zap tags, clients wishing to zap it SHOULD calculate the lnurl pay request based on the tags value instead of the event author's profile field. The tag's second argument is the hex string of the receiver's pub key and the third argument is the relay to download the receiver's metadata (Kind-0). An optional fourth parameter specifies the weight (a generalization of a percentage) assigned to the respective receiver. Clients should parse all weights, calculate a sum, and then a percentage to each receiver. If weights are not present, CLIENTS should equally divide the zap amount to all receivers. If weights are only partially present, receivers without a weight should not be zapped (weight = 0). 

 is there any client that implemented/leveraged this? 

 I know that amethyst on Android does 

Example zaps to this note will go 90% to you and 5% to opensats (if zapped via amethyst and any other client that support it)