require 'benchmark'

array = Array.new(1_000_000, { id: 'key' })
values = ['.p12', '.pfx']

Benchmark.bmbm(7) do |bm|
  bm.report('to_h') do
    array.map do |prop|
        [
            prop[:id],
            values
        ]
    end.to_h
  end

  bm.report('inject') do
    array.inject({}) do |acc, prop|
        acc.merge("#{prop[:id]}" => values)
    end
  end
end

Rehearsal -------------------------------------------
to_h      0.400000   0.020000   0.420000 (  0.435615)
inject    2.090000   0.110000   2.200000 (  2.209907)
---------------------------------- total: 2.620000sec

              user     system      total        real
to_h      0.300000   0.160000   0.460000 (  0.449012)
inject    1.980000   0.090000   2.070000 (  2.075692)