Voltage dividers will work well for low currents and well defined constant loads. 1.5A is too high of a current for good regulation and reasonable heat dissipation with a voltage divider.
The choice between linear regulator and switching regulator depends on the application. Generally linear regulators are less noisy, less efficient, and dissipate more heat. Switching regulators are more efficient and cooler at higher load current. Switching regulators work well when they have a high differential (input to output) voltage compared to linear regulators.
The LMZ12002 module is a good part but requires selection of many external components. Also, looking at the datasheet, it is difficult to tell if it will work with a low (1V) input to output differential voltage. The graphs show the lowest differential voltage of 2.2V. The minimum input voltage would be 6.2V not 5V for 4V output.
The NQR002A0X4Z is another prebuilt module with a lower differential voltage requirement of about 0.7V. The input voltage must be at least 4.7V for it to regulate to 4V at 2A. And it is a little cheaper and it still has pins. There lots of surface mount options.
NQR002A0X4Z at Digikey
Minimal parts count is a single resistor, RTrim. However, it is best to add a 10uF or 22uF low ESR cap (ceramic) to the input and the output. Connect them close to the pins.
12/(4-0.6) = 3.52941k
closest value is 3.57K, 1%
The C-tune and R-tune can be left out for general purpose use. They are for speed.
Leave the enable pin open and the part will turn on. Or connect it to Vin through a 10k resistor to be sure.