Size: 24.6 diameter, Model: AP621, 61.4mm length., Output: Up to DC 5V 3.6A, Weight: 54g, Color: Sliver, Type: Dual USB Car Charger, Input: DC 12-24V.
Basically copy coupon, view price history or create e-mail price alert. You probably want to know what is the best price?
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($15.29): BGAFF10OFF
2. ($15.99): 13f142
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): TTxBG10, aff7off, BG3CSUM, bgssaff9, BGEScgr, AFfbG10, 502C6B, BGBFCR02, BGCITYADS2019, BGMPB2020, bGhOnEy10, BGXMI15, BGdragonBoat, BGSS10%SW, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi ZMI Car Charger 18W Display QC3.0. The lowest price was: $9.34.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).