When To Complete A Cash-Out Refi On A LTR

Hi, I have a LTR that I purchased earlier last year that according to Zillow has appreciated 45%. I would love to reinvest some of the equity into another property through a cash-out refi. What indicators do you use to determine if a property is in a position for a cash-out refi and how do you determine the current value of the property? I've been using zestimates to determine property values but not sure how accurate it is. Thank you for your feedback!