"Is the equipment rating in line-neutral volts or line-line volts?"

Nominal voltages for three-phase equipment are always specified as line-to-line voltage, regardless of if the equipment is intended for connection in delta or wye.

In your case, the transformer is 13,800V line-to-line LV, and 120,000V line-to-line HV.

Occasionally, both the line-to-line and the line-to-neutral voltage are specified; as in a three-core cable labelled "11/6.6kV", with 11kV worth of insulation between phases, and 6.6kV of insulation between each phase and ground.

What is the turns ratio across a delta-wye transformer?

In a three-phase Dy transformer with voltage ratio 1:1, the delta winding will have \$ \sqrt{3} \$ more turns than the wye winding.

The zero sequence has no phase shift between voltages. Therefore on the delta side of the transformer, voltages will remain equal at all times between terminals, which means no current can flow through these terminals.

In general; no current can flow into a delta when fed by a zero sequence source.