In a small sauce pan, bring honey and water to a boil. Add rhubarb, strawberries, shallots, and thyme sprig. Continue to boil for another 5 minutes, stirring often. Reduce heat and stir in vinegar and lemon zest. Simmer for about 8 minutes until reduced by half and rhubarb is very tender. Remove from heat, take out thyme sprig and allow to cool.