It may would be tough.
The placement of "would" after "may" when we refer it for future, is it appropriate?
Every complete clause has one, and only one, verb in finite form. When the verb built with one or more auxiliary verbs before the main verb, as in a passive or progressive or perfect construction, the finite verb is always the first auxiliary in the chain. The rest of the verbs in the chain must take one of three non-finite forms (which form is determined by the preceding auxiliary). These non-finite forms have no tense, person or number; all of which are inferred from the context:
Thus, almost all English verbs have between four and eight different forms to play six different roles, three finite and three non-finite. But there are a few special verbs which linguists call defective, because they have only one or two forms and they play only three of the usual roles.
These are the modal verbs: can/could, may/might, must, shall/should will/would. These verbs have only two forms, both finite: a present form (without a distinct 3d person singular) and a past form. They have no non-finite forms: no present participle, no past participle, and no infinitive.
Consequently, in Standard English these verbs can only stand at the head of verb chain, as the single finite verb in the chain, never in a second or later position. And there can only be one of them—they cannot be chained or ‘stacked’.
These rules are not always observed in dialect. As wordsmythe notes, you might encounter constructions like I might could do that or He mighta shoulda told you in speech or in written dialog. But those are not acceptable in Standard English, either written or spoken, unless they are used ironically.
No, you should not use both together.
"May" indicates that you're less sure of the outcome - it's possible it will be tough, but who knows.
"Would" indicates a greater certainty that it will be tough.