Phase 1 project setup and mechanical constraints
Load the "Raspberry Pi Zero Shield Template". Adjust the board outline to 68mm x 45mm to fit the 4th Generation iPod chassis. Set the maximum Z-axis height constraint to 19mm. Configure a 4-layer standard stackup. Define a 0.2mm keepout zone. Delete any standard 40-pin female through-hole headers from the template, as the Pi Zero 2 W will be flush-mounted without headers.
Phase 2 primary power and star ground topology
Add the Adafruit BQ25185 USB/DC/Solar Charger with 5V Boost (Product ID: 6106). Connect the BAT pad to a JST-PH 2.0 connector for a 3.7V LiPo battery. Connect the 5V pad to a new net named +5V_DIRTY. Designate the GND pad of the BQ25185 explicitly as STAR_GND. Route the +5V_DIRTY net through an in-line physical master power switch.