Place the shortening and butter into your stand mixer with the lemon zest and salt. Mix until smooth and incorporated, about 2 minutes.
Add 2 cups sugar and ¼ cup pineapple juice and combine. Continue to all in the remaining sugar, juice and cream until thick and at the consistency you want. Add more sugar if you want a thicker frosting or more cream if you want a thinner frosting.
Store in an airtight container and place it in a cool place overnight.