I have defined a sample scenario based on your requirement as below and could see it is working

You can work on the same for accounts and once understood , you can apply the same logic to your fields.

Scenario : creation of a New account via Quick create

Conditions :

1) If Prospect check box is active , then Phone Number field is Not mandatory
2) If Prospect check box is not active , then Phone Number Field is Mandatory , * indicator is shown and Save Fails with Error message

Actions Taken :

Go to the Field Phone in Adapt
Select Change Properties
Select the hyperlink rule next to Mandatory
Against the Rule Name , select Create New rule and Enter a rule name.
Identify the Field from Field name , my field is Prospect which is a checkbox , I will select the Field Prospect which is Identified as Root.Prospect
Select Functions and define a rule with IF as condition in the format : IF(logical_expression, value_if_true, value_if_false)
So while I define my rule ,it will be IF(Root.Prospect, true, false)
Click on Apply and Save

So the Rule defined here satisfies the conditions above and completes the scenario with conditions.